COVID-19 Vaccines: Facts vs. Fiction

Written: 2020/12/09

  • What about the long-term effects of the COVID-19 vaccines?
  • What does it mean if a vaccine is “95% effective”?
  • Do any of the COVID vaccines contain nanoparticles?

It can be difficult to find straightforward explanations that are not written in scientific terms for these types of questions. This post outlines some simplified answers to a few COVID-19 vaccine questions, along with citations to corresponding scientific sources or authoritative sources.

This post itself is not meant as any sort of authoritative guide, but rather as an approachable resource to point you in the direction of actual, reputable sources. Note that all the underlined text is a clickable link to a source, not just underlining for emphasis. That’s how the sources are cited here.

In the menu below, each question should be “clickable” to navigate to that answer within this post. This is a long document, so please do make use of those hyperlinks below to go to a particular question.

<<This post is absolutely, definitely, NOT medical advice.>>

None of the information in this post is medical advice for you. My goal here is to provide you with links to some helpful references answering common questions related to the COVID-19 vaccines, not to tell you what is correct for your personal health circumstance. The decision whether to take a COVID-19 vaccine is a personal decision, but it should be one that is made based on the available evidence and in consultation with your physician.

If there are any inconsistencies between the information in this post and information from reputable sources like the CDC/WHO/etc., consider this post to be incorrect and those authoritative sources to be correct. (and let me know, so I can fix it).

Who sponsored this post?

This post is not sponsored in any way, shape, or form by any manufacturers of COVID-19 vaccines, by any government agencies, or by anyone, actually. I have declined the option to get paid per number of pageviews on this post, because I didn’t want this post to go behind any sort of paywall. I don’t hold stocks or any other form of financial interest in any companies developing COVID-19 vaccines, and, to be quite honest with you, I don’t really care whether you personally end up choosing to get a COVID-19 vaccine.

The purpose of this post is to provide a convenient place with some links to scientific resources providing answers to some of the most common questions and myths about the COVID-19 vaccines. I would encourage you to use this post as a jumping-off point to learn about new topics or potential resources. If you notice an error in this post, feel free to reach out at

If you find this post to be a useful resource and would like to support my science communication efforts, you can buy me a coffee on my page at this site (linked), and my venmo/cashapp is @drnocphd, but please feel no obligation to do so, that is not why I made this post.

You can find me at @dr.noc on Instagram. Below is the list of clickable links to specific questions, or you can scroll past it and just read through the sections if you have some time on your hands.

List of questions

(note, these table of contents links below currently only work on desktop browsers, not mobile for some reason. If you’re on mobile, scroll down to your section of interest. Looking into how to fix that…)

How do vaccines work?

Briefly, how do vaccines work? There are many different “types” of vaccines, but they all work in basically the same way:

  1. prepare a less-dangerous version of a virus or bacterium (or perhaps just a small protein from the pathogen)
  2. show it to the immune system
  3. wait 2 weeks for the immune system to prepare its response.

The immune response to a new target takes about two weeks to give you protection. (This is why vaccines are mostly only helpful if you get them prior to an actual infection, not once you are already infected).

When you get a vaccine injection for a virus, it usually contains either a small piece of a viral protein or a non-infectious version of the virus. This allows your immune cells to recognize the shapes of the molecules on that virus. Over the next few weeks, those immune cells grow more of themselves and produce antibodies so that when they encounter the virus in the future, they are ready to defend against the infection. Since the vaccine itself does not contain the actual infectious virus, this allows your immune system to “train” against the virus without posing a risk of actually causing the disease.

Link to CDC: “how do vaccines work?”

How do mRNA vaccines work?

Traditional vaccine formats often are based around a viral protein, such as the spike protein on the outside of the virus that causes COVID-19. mRNA vaccines are slightly different; instead of injecting that protein directly, they include a small piece of the RNA that can be used to produce that piece of the virus (in this case, the spike protein of the virus that causes COVID-19).

There are a lot of misconceptions here:

The mRNA vaccines do not encode the entire virus — they only lead to the production of a small piece of the outermost part of the virus. As a result, they are not infectious, and do not self-replicate.

One common question is whether the mRNA vaccine can change your DNA. They cannot. When the mRNA vaccine is injected into your arm muscle, it gets taken up by the cells in your arm, but never enters the nucleus of the cell, where your DNA is stored. Instead, the mRNA just sits outside in the cytoplasm, where the ribosomes use the mRNA as a set of “instructions” for how to manufacture the viral spike proteins. The viral spike protein is then presented to the immune system as something that is “foreign” to your body, and the immune system trains up its response for how to fight it if it sees it in the future.

If changing your DNA was as easy as injecting some mRNA, we would have better solutions for a lot of existing genetic diseases.

Importantly, mRNA does not stay in your cell forever, it starts to get degraded after it has been used to make some of the spike protein it encodes. Receiving an mRNA vaccine is a temporary event that does not actually change your genes. Some people may have heard that the mRNA will “encode new cells,” but the mRNA does not encode cells, just the viral spike protein, and that mRNA is gone after it has been used to make some copies of the viral protein.

So, from start to finish,

  1. the mRNA vaccine is administered
  2. mRNA vaccine is taken up by your cells (not into the nucleus)
  3. mRNA is used to make some of the viral spike protein
  4. viral spike protein is used to train the immune system in preparation for future actual infections
  5. mRNA degrades and is eliminated from the cell

At no point in this process does the mRNA vaccine change your DNA or lead to the production of the actual virus that causes COVID-19.

From the CDC: A closer look at how mRNA vaccines work

What does it mean if a vaccine is “95% effective”?

You may have heard that a vaccine is “95% effective,” but what does that number actually mean? To put it simply, it means that your risk of getting symptomatic COVID-19 is reduced by 95% from whatever it was without the vaccine (a 20-fold reduction, in this case).

It’s probably helpful to take a step back and describe how the COVID-19 trials are designed. The COVID-19 vaccine clinical trials are double-blinded, placebo-controlled studies. What does that mean? When people sign up to join the studies, they are told that they will be randomly assigned to receive either the actual COVID-19 vaccine or a placebo (a sham-injection of regular salt-water). The trick is that neither the participant nor the medical providers know if the patient got the vaccine or the placebo… this information is only revealed at the very end of the trial.

The purpose of this design is to make sure that people who received the vaccine do not behave differently than everyone else. For example, you might imagine that someone who knew that they got the real vaccine might be more confident meeting up with friends, going to crowded areas, etc., exposing themselves more, which might make it look like the vaccine was not working.

By obscuring the knowledge of whether each person in the trial received the placebo or the real vaccine, it makes it easier to compare the actual efficacy of the vaccine (how well it’s working): if there are way fewer COVID-19 cases among the people in the vaccinated group compared to the people who got the sham-injection, that means that the vaccine is probably protecting them.

For example, a big phase 3 trial may involve vaccinating ~15,000 people with the real vaccine, giving another ~15,000 a salt-water placebo injection (with no vaccine), and then waiting to see which group ends up having more diagnoses of COVID-19 over time. They do not intentionally expose people to the virus, they just wait and observe them after going about daily life. If there is a big difference in the rates of COVID-19 in the vaccine vs. placebo group, you know that the vaccine is helping prevent disease.

Let’s look at some real data as an example here. In the recently reported FDA vaccine clinical data packet for the Pfizer trials (freely available for you to read at this link), they compared the relative rates of infection over time among the vaccinated group (blue line) and the placebo group (red line), shown below. An increase on the Y-axis means that there were more COVID diagnoses. The X-axis represents the number of days after the vaccine or placebo was administered. Two things should be clear from this chart:

1) The vaccine takes ~14 days after the first dose to start working (like we discussed above). This is clear in the below data chart because, for the first 14 days, there is a similar rate of increasing COVID-19 cases across both the red and blue groups.

2) After 14 days, the rate of new COVID-19 infections in the vaccinated group (blue line) is way lower than the placebo group (red line), meaning that there were far fewer new infections in the blue/vaccinated group.

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The “blue” (vaccinated) group had far fewer COVID diagnoses than the red (placebo) group, after they were at least 14 days’ past their first dose of vaccine.

Why would anyone want a vaccine that is 95% effective if they personally have a 99% chance of survival?

If you haven’t read the prior section yet, I would recommend that you read that one before this one. Understanding what they mean by “the vaccine is 95% effective” is crucial. At face value, if you just compare numbers, it may seem strange to want to take a vaccine that is “only” 95% effective if you think your personal rate of survival is already 99%, based on your estimate of your own risk factors.

However, a vaccine effectiveness of 95% means that it reduces your risk by 95% from whatever it would have been if you didn’t take the vaccine. It definitely does not mean that there is a 95% chance that it protects and a 5% chance that it gives you COVID-19, or anything like that. So, if you think you had 99% chance of being fine before, now it’s 99.95% — a pretty good upgrade. Further, the “99%” is only discussing mortality. It may be even more attractive if you also have a 95% reduction in risk of developing lung scars, brain damage, heart/vascular damage, etc.

Even if a hypothetical vaccine was only 50% effective, that would still be decently helpful, because it would take whatever risk you had without the vaccine and cut it in half. We will have to wait to see how long the protection lasts from the COVID vaccines, but the above data from the Pfizer study suggests that they’re providing pretty good protection for at least a few months.

Link to full Pfizer vaccine data packet (long read, but very informative for behind-the-scenes insights. Not really behind the scenes, I guess, since it’s public information.)

Link to long-term effects of COVID

What about the long-term effects of a COVID-19 vaccine?

Ah, the big question — how in the world could we know about the long-term effects of a COVID-19 vaccine if we have only been testing them for less than a year? Unfortunately, there is no getting around the fact that we will not be able to directly observe long-term outcomes from either a COVID-19 infection or a COVID-19 vaccine until we wait a few years. For now, we will all have to make a judgement call on which of these two options seems like it is going to pose greater health risks in both the short- and long-term: vaccine vs. true COVID-19 infection. Let’s look at the evidence for what we know about the infection and the vaccine, starting with the COVID-19 infection.

Most people who have COVID-19 end up being totally fine (no one disagrees about that). Let’s put that into estimated numbers, though, and say that you personally might have a 99.5% chance of survival (meaning just a 0.5% chance of death) and a 2% chance of hospitalization. Please note that these estimates are rough, and are meant to convey a general way of thinking about these risks/benefits.

What happens in the relatively unlikely event that you happen to catch a bad case of COVID? You may survive, but there can be some significant lasting effects of the infection that stick around long after you have cleared the virus.

These long-term effects of COVID infections can include lung scarring (pulmonary fibrosis), infection of your heart muscle, damage to your arteries and veins, brain damage, lasting loss of smell/taste, and “long hauler” symptoms lasting for many months. Back in the SARS outbreak in 2002, some patients who recovered from the initial infection experienced decreased lung function for years after they had cleared the virus.

Right now, it seems that somewhere in the range of 10% of patients with confirmed COVID-19 experience some form of lasting symptoms. After accounting for the fact that some infections may go undiagnosed (maybe as many as 90% of infections are unaccounted for), perhaps we can estimate that closer to 1%-2% of all infections lead to some type of long-lasting symptoms. Right now, it is difficult to say exactly what the long-term effects of the COVID-19-induced lung scarring, heart damage, brain damage, or vascular damage will be… but let’s be realistic.. you probably want to avoid these things, regardless of how old you are (they can happen at any age).

In comparison to the effects of COVID-19 infection, what has happened with the participants in the COVID vaccine clinical trials? It’s important to note that the vaccines certainly do result in side effects for some people (and sometimes those side effects can be quite severe), but they only last for a few days. Some people experience fatigue, muscle soreness, fever, or some other effects (more on that in section below).

As a thought experiment, imagine that 30,000 people receive COVID-19 vaccines. Based on the clinical data we have from the trials, those vaccinations would cause zero deaths. Many of the patients, however, would experience side effects such as fatigue, fever, and soreness, some of which would be quite severe, but resolving within a few days. Some patients with a history of having really severe allergic responses may be at risk of bad allergic reactions.

Let’s compare that to what would you expect to happen if you were to infect 30,000 people with COVID. At a 99.5% survival rate, 150 would die, and hundreds more would be hospitalized (but survive) or be left experiencing various long-term effects of COVID-19 such as lung scarring, heart damage, lasting loss of senses, and long-hauler symptoms.

Even if you estimate closer to a 99.9% chance of surviving COVID-19 (instead of 99.5%, as used in the calculations above), 0.1% of the 30,000 is still 30 deaths in the “infection” group compared to the expected 0 deaths in the “vaccine” group.

These types of comparisons are how the regulatory people weigh the benefits versus the risks of the COVID-19 vaccines. At the end of the day, you will have to make a personal judgement call comparing the vaccine against an actual COVID-19 infection, because we won’t be 100% sure of the long-term effects of either COVID-19 infections or the vaccines until we wait.

The FDA briefing document on the Pfizer vaccine data has an excellent description of the observed risks and benefits from the clinical trial data, going into great detail to talk about what specific adverse events happened after vaccination, the ways that they analyzed how well the vaccine worked, the demographics of the study, different analyses broken down by age group, etc.

What types of adverse effects would you expect to possibly happen with the COVID-19 vaccines?

As discussed in the last section, there are side effects from the vaccines. Some of those side effects can be severe in some people. To give you an example from the Pfizer vaccine, AP produced this great graphic based on the clinical results. You will see that side effects are broken down by age of patients, type of side effect, as well as severity of the side effect.

The grey bar is the sum of all levels of severity for that symptom (the total percent of people who experienced mild OR moderate OR severe fatigue was ~59.4% under age 55, for example). Broken down with the yellow bar at the top, then, for example, 21.1% of people age 18–55 experienced mild fatigue:

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But what about other types of side effects? There are a few other types of outcomes that have a risk of happening with any vaccine development program. The big ones are inflammatory/allergic reactions, antibody-dependent enhancement, and Guillain-Barre Syndrome. The important point here is to think about the timeframe in which these bad reactions would happen (if they were going to be a problem for a given vaccine). The below effects don’t occur years after vaccination. If they’re going to happen, these are on the order of days or months.

Inflammatory/allergic reactions happen swiftly after receiving a first or second dose of the vaccine, typically within minutes but up to about a day after a vaccine. As such, allergic responses are a definite short-term concern, particularly in people with a history of bad allergic reactions, but are not a long-term safety concern.

Reference: The development of allergic inflammation

Antibody-dependent enhancement (ADE) is an effect that has been observed to happen in rare cases for some other diseases. To explain it simply, it is where having an immune response against a virus that only half-way recognizes that virus (but does not neutralize it completely) actually makes your second exposure worse, because the antibodies make it easier for the virus to enter certain types of cells.

This has been observed in the cause of dengue virus, for example, and is something that is closely monitored for during any vaccine development effort. The important question with ADE is when you would be able to tell if it was happening (if it was happening at all). If the patients who received the vaccines were actually having worse disease outcomes than the people who received the placebos, that would be quite clear from the clinical trials.

Instead of there being reduced numbers of infections in the vaccinated group and reduced severity of infections, the vaccinated group would actually do worse, compared to the people who got the placebo. This would be unfortunate, but would be quite clear from the vaccine clinical trial results, and there is simply no evidence to suggest that ADE is happening with the COVID-19 vaccines — the overall effect is the opposite: people who receive the vaccine have far fewer symptomatic infections and less risk of severe disease.

Guillain-Barré Syndrome (GBS) is an inflammatory type of reaction that can occur following either an infection or, in some rare cases, after vaccination. Most cases usually start within a few weeks after a respiratory or gastrointestinal viral infection. Occasionally, a surgery can trigger the syndrome. In more rare cases, vaccinations may increase the risk of GBS. To give you a frame of reference here, the seasonal flu vaccine may increase risk of GBS by about 0.000001% (literally about one in a million). However, there is a small chance that any new vaccine could increase risk by more than this, so it’s something to watch out for in clinical trials. Since most cases of GBS happen within ~6–8 weeks of an infection/vaccination, if the COVID-19 vaccines were causing significantly increased risk of GBS, this is something that you would expect to see within a few months of vaccination, not years down the line. Actual COVID-19 infections have been noted to lead to GBS.

Detailed overview of mRNA vaccines.

Do mRNA vaccines change your DNA?

Short answer: no, mRNA vaccines cannot change your DNA. There are two big reasons why this does not happen:

  1. The mRNA will only be present in the cytoplasm of your cell. It does not have the set of transport markers that are required to gain entrance to the nucleus (where your DNA is stored), so it can’t even get close to the DNA in your cell.
  2. The mRNA is actually not very stable and will be degraded inside your cells soon after being taken up and used to make the spike proteins.

The mRNA vaccines are administered into your arm muscle. Once the mRNA are inside the cells, they are used to make a protein piece from the SARS-CoV-2 virus. After a few copies of the protein piece is made, the cell breaks down the mRNA and gets rid of them. Then, those pieces of viral protein get shown to your immune system, which then spends about 2 weeks building up a protective antibody response in case it encounters that viral protein again (such as in the case of a future infection).

This is essentially just a safer version of what happens during an actual infection with the SARS-CoV-2 virus, because the mRNA is just encoding that single piece of spike protein and does not encode the rest of the virus or cause the generation of any actual viral particles.

Detailed review of mRNA vaccines #1

Detailed review of mRNA vaccines #2

Is immunity from an actual infection better than immunity from the vaccine?

No, immunity from an infection is not necessarily better than from a vaccine. For example, a recent update from the Moderna mRNA vaccine was published December 3rd, 2020, and found that, among a sample of 34 patients who received vaccines in some of the earlier trials, all of them still had antibodies 3 months after their final booster shot. This sample of patients included some patients who were over the age of 71, who also exhibited durable antibody responses. From looking at the chart of their antibody levels over time (Figure 1 in that study linked above), it is clear that the levels are slowly going down over time, but this indicates that the vaccine should provide at least several months of protection.

A similar type of data analysis of antibody levels in patients who received the Pfizer vaccine compared the amount of antibodies that the vaccinated people had against the amount of antibodies in the blood of people who had recovered from an actual COVID-19 infection, and found that the vaccine appeared to actually lead to 2x-4x more antibodies compared to a set of recovered patient samples (after real COVID-19 infections). Combining these findings with the evidence of protection against symptomatic COVID-19 seen from the clinical trial results, it seems that the immunity that you gain from the vaccines has a good chance of lasting for at least a few months. However, looking at antibody levels alone doesn’t tell the whole story, so the real comparison will come from following the clinical trial patients in the months to come to see how long they are protected.

Is this the first mRNA vaccine that has been tested in clinical trials?

Nope. mRNA vaccines have actually been tested in clinical trials (in humans) for ~5 years. This linked review article, published in Feb 2020, includes data on the 12 separate clinical trials for mRNA vaccines for infectious disease that were, at the time, either in progress or had already been completed. If you are interested in doing some more detailed reading to learn how mRNA vaccines work, there is a nice Nature review article from back in 2018 at this link.

The link at the end of this sentence has the results from one prior mRNA vaccine for influenza that demonstrated good safety and generation of immune responses in a phase 1 trial, which enrolled participants between December 2015 and August 2017, and was published in 2019. Here is another clinical trial posted in 2017 that enrolled subjects to evaluate an mRNA vaccine against Zika virus.

However, it is certainly true that mRNA vaccines have never been tested before on the scale that they have been tested this year. The only reason I bring up these examples is that a lot of people seem to think that no one has even ever tested an mRNA vaccine in humans prior to this pandemic, which is simply not the case.

Are the COVID-19 vaccines “live” vaccines?

No, the COVID vaccines that you have been hearing about recently are not “live” vaccines. Live vaccines include a less-dangerous version of a virus that is able to infect some of your cells, but has been weakened so that they don’t cause full disease. This is very different from something like an mRNA vaccine, which does not even include a full virus at all — it only includes the small piece of mRNA that codes for one particular protein from that virus (like the spike protein). The mRNA does not encode the instructions on how to produce the full virus, does not change the DNA in your cells, and will be degraded within the cell after it is used to make viral protein.

In the future, scientists may test whether they can get even better results using a live, weakened virus as a vaccine for COVID-19, but that’s not the case for any of the current leading vaccine candidates.

Can COVID-19 vaccines actually give you COVID?

No, as discussed in the prior section, the COVID-19 vaccines can’t give you COVID-19, because they don’t actually contain the full virus. The mRNA vaccines just include the information for the spike protein from the virus and are non-replicating. Once the mRNA has been used to make some of the spike protein, they start to get degraded and are soon totally eliminated.

Importantly, it takes about two weeks for your immune system to build up a protective response after vaccination. This means that there is an inevitable time period where you’ve already had the vaccine, but haven’t yet built up enough immunity to prevent infection. For example, if you got the vaccine today, and someone infected with COVID coughs on you tomorrow, there is still an extremely high risk that you could be infected. This is true for all vaccines… and leads to quite a lot of confusion with the seasonal influenza vaccine, for example. If someone does not know that it takes 2 weeks for the immunity to kick in, and they catch the flu three days after getting their flu vaccine, they may think that the vaccine gave them the flu, but in reality the immune system just has not had enough time to build up protection.

We will probably run into some similar confusion with the COVID-19 vaccines, where someone is going to get their first COVID-19 vaccine injection and then develop COVID symptoms and get a positive test result a few days later (long before the 2-week immune-training period is done). I’m crossing my fingers that we’re not going to see headlines like “WOMAN, 66, DEVELOPS COVID-19 THREE DAYS AFTER RECEIVING HER COVID VACCINE.” … because this exact scenario is definitely going to happen, simply as a matter of chance, if a few million people are getting a vaccine in the next month or so.

Can COVID-19 vaccines be safely used if you are immunosuppressed?

For specific questions like this, it is always best to consult your physician. When it comes to people who are on immunosuppression and the COVID vaccines, there are two big types of questions: 1) is the vaccine potentially going to cause COVID in people with suppressed immune function? and 2) will they get any protective benefit from the vaccine?

The answer to #1 is no, because the vaccines do not contain live, replicating viruses and therefore can’t cause actual COVID-19. That being said, you should check with your doctor about whether any of the other side effects of the vaccines may be particularly bad in combination with your condition (like a risk of severe fever), and come up with a plan. The answer to #2 is less clear, because each person who is immunosuppressed has a different level of immunosuppression. Responses to vaccines can vary a lot depending on the underlying immune disease or on what types of immunosuppressive drugs you are taking. For some more detailed information about immunosuppression and the COVID vaccines, I would refer you to this excellent article from

Will a COVID-19 vaccine make you test positive on the COVID-19 tests?

No, receiving a COVID-19 vaccine will not make you start testing positive on the COVID-19 tests that are used to tell if you are currently infected. Those PCR and antigen-based tests are designed to look for the presence of viral RNA or viral proteins in your respiratory swab samples, and the mRNA injection into your arm muscle will not cause a positive result on those tests.

However, the vaccine will lead to the production of antibodies, which will make you test positive on antibody-based tests for COVID-19, after your immune system has had a week or two to build up its response. These antibody tests (blood tests) are not used to tell whether you are currently infected/infectious with COVID-19 and are totally different from the nose/throat/saliva swab-based PCR tests and antigen tests.

Are the COVID-19 vaccines safe in children?

So far, we do not know whether the vaccines are safe/effective in children. The typical pharmaceutical process is to first demonstrate safety/efficacy in adults, and if it looks good there, then you start testing in children. With the COVID-19 vaccines, since the leading candidates have shown good safety in clinical studies in adults, they have recently begun to be studied in children aged 12–17 years (Moderna studies in children | Pfizer starting studies in children). If those studies’ results show that they are as safe as they have been in adults, they will then move on to see if it is safe in younger children.

Are the COVID-19 vaccines safe in pregnant women?

The short answer is that we do not know if the vaccines are safe/effective in pregnant women because they have not been included in the clinical trials to date. This decision is a double-edged sword. Since pregnant women were not included in the clinical studies to protect against unknown potential harms, but we also now have very little clinical data to inform decisions moving forward.

This is complicated by the fact that pregnant women are potentially at increased risk for severe COVID-19-associated illness and death compared to non-pregnant women, so the benefits of being protected via vaccination could be particularly important, but there are just no clinical data that are available yet. Talk with your doctor.

Do any of the COVID-19 vaccines have nanoparticles?

Well, yes… but they’re really not that exciting. There is a lot of confusion over what nanoparticles are. In contrast with popular perceptions of nanoparticles as basically being nanorobots, the nanoparticles used in the mRNA vaccines are actually pretty simple and have been used in some other types of drugs for decades.

Specifically, these nanoparticles are lipid (i.e., fat molecule) nanoparticles. In essence, lipid nanoparticles consist of a lipid bilayer (like the one that makes up your cell wall) that forms a little sphere, and there is a small pocket of water inside the sphere. If you have a fragile molecule (like RNA) that you want to protect until it gets to its intended site (like inside of a cell in your arm muscle), you can put that fragile molecule into the middle of that lipid sphere. The lipid bilayer protects it from degradation and helps the RNA get into your cell before it gets degraded. That’s it — that’s the function of the nanoparticles. There are no robots involved, no nanoscale electronic software, etc.

Off-topic: The first lipid nanoparticle drug that was approved is called Doxil, an anti-cancer drug, and was approved back in 1995. It has the same type of lipid nanoparticle, with a bilayer surrounding a water-filled core. Instead of RNA in the center, those particles are filled with a cancer drug called doxorubicin. By putting them into the lipid nanoparticle, it actually helps keep them hidden until the entire particle makes it to the tumor site, which means that the doxorubicin molecules cause less off-target toxicity (like to the heart). There have been plenty of other types of lipid nanoparticles investigated and used in clinical practice, but my main point here is that “nanoparticle” is a buzz-word that is often incorrectly interpreted to mean “small robots,” when it’s actually usually just little spheres of fat molecules used to protect some cargo.

Here is a good Reuter’s article on the difference between the true meaning of “nanoparticle” and the incorrect interpretation of “small computers/robots”

If you are interested in doing a deeper dive into current trends in the use of nanoparticles for the treatment of various diseases, this link will lead you to a rather detailed review article.

Do the COVID-19 vaccines have microchips/trackers?

Nope — the vaccines (which are being produced at a cost of roughly a few dollars per dose) do not have microchips that may record and transmit your biometric data. For this one, I recommend that you read the detailed report from Reuters that describes one possible origin of this myth, as well as investigates the various video clips that were edited together to try to convince people that Bill Gates wants to track you (when the original footage was actually talking about him wanting to track the vaccine… like to keep track of the supply chain of vaccine doses as they are shipped around the world).

Suffice it to say that there is a big difference between putting a tracking label/chip on the outside of the glass vial of the vaccine, which could be scanned during shipping & storage to keep track of information related to manufacturing conditions & lot number, vs. putting a tracking device inside of the actual vaccine… which no one has proposed and is not part of any of the actual COVID-19 vaccines.

Can you benefit from a COVID-19 vaccine if you have already been sick and recovered with COVID-19?

Probably so, to reduce the risk of another infection in the future, since we know that your immune protection slowly declines over time and there have been documented cases of people getting re-infected within a few months of their first infection (although confirmed re-infections remain rare, which is good, and suggests that most people will be protected for at least a few months).

I do not know of any way that getting a vaccine after recovering from a first infection would help reduce any long-lasting symptoms of that first infection, since those symptoms can persist long after you have cleared the actual viral infection.

Will the COVID-19 vaccine affect fertility?

No evidence suggests that the vaccine is in any way associated with infertility. In the Pfizer vaccine trials, there were actually a few women who unintentionally became pregnant after being vaccinated: 12 in the vaccine group and 11 in the placebo group. In the 12 pregnancies in the vaccinated group, there were no observed adverse effects on the pregnancy. This is just a small amount of accidentally-collected data from the trials, but perhaps it provides some small amount of reassurance against the vaccine/infertility concern.

You may have seen the circulating claim that there is a part of the COVID-19 spike protein that has a similar amino acid sequence to a human protein called syncytin-1, and the claim therefore suggests that immunity against the spike protein will cause immunity against syncytin-1, which could theoretically make you infertile. This seems wrong for a number of reasons and has been criticized by a number of scientists. Unfortunately, to address this claim requires that we get a bit more scientifically detailed, so skip ahead to the next question if you don’t care about some more technical discussion:

Finding amino acid alignment is not a big deal in the absence of any other evidence, and it is actually really easy to find regions of amino acids that overlap between two large proteins. In fact, if you compare the sequence of the spike protein to a bunch of other proteins in the body, there are similar (or greater) levels of overlap as that seen with syncytin-1, such as with hemoglobin, collagen, actin, etc. This is statistically common; you would expect to see matching amino acid sequences here and there when comparing any two large proteins.

Further, you can find comparable similarities if you compare the amino acid sequences of syncytin-1 and proteins from common pathogens like influenza, E. coli, streptococcus, and a few of the seasonal coronaviruses (NL63 and 229E). If the claim were true that simply having some amino acid alignment between the SARS-CoV-2 spike and syncytin-1 meant there would be cross-immune activity, then you might expect that same logic to apply to all those other pathogens and to all the other proteins in the body that also have regions of overlapping amino acids.

If there was homology between the structural features of syncytin-1 and the spike protein at a larger scale (not just sparse amino acid alignments), then it could be possible that immune responses could recognize the two targets similarly, but there is no evidence either of such large-scale homology or of overlapping immune cell recognition, as far as I have seen. Even if there was homology, you would expect mechanisms of T cell tolerance to reduce the risk of induction of an anti-self response. As far as I’ve seen, the only “evidence” produced to support this claim so far is showing some back-of-the-napkin amino acid similarities, which is not convincing on its own.

The immune system has a lot of checks and balances to try to avoid attacking your own body, and a few short regions of overlapping amino acids alone isn’t enough to cause bad reactions.

Edward Nirenberg has also written up a detailed article with some more perspective in response to this particular claim.

Ultimately, we will require more clinical data following people who receive the vaccine and then later choose to become pregnant, but so far I am not aware of any actual evidence that this is a reasonable concern.

How were they able to come up with a COVID-19 vaccine in less than a year, but not a cure for cancer?

Some diseases are easier to treat than others. Cancer cells are inherently very similar to healthy cells, plus just a few mutations. This means that it is extremely hard to specifically target the cancer cells, but do not target the healthy cells, and this is why chemotherapy drugs often have such awful side-toxicities to the rest of the body. Further, “cancer” is really an umbrella term that includes a wide range of different diseases, and different types of cancers will require different types of “cures.”

Review article describing progress on the development of cancer vaccines

Why does chemo cause side effects, from

Will the COVID-19 vaccine contain blood?

No. You may be thinking of convalescent plasma, which is totally different from a vaccine. The current vaccines contain a few types of lipid molecules (fat molecules), the non-replicating mRNA, and some salt/sugar. (Yes, the ingredients are published if you’d like to take a look for yourself.)

Will the COVID-19 vaccine have the virus that causes COVID-19 in it?

No, the current vaccines do not contain actual live COVID, and therefore can neither lead to a real COVID infection nor give you a positive COVID test result.

Will the COVID-19 vaccine end the pandemic?

It seems like the answer is “not immediately,” since there will be a limited number of doses at first. In the people who are high-risk, who receive the vaccines first, we might expect those vaccinated groups of people to have a substantially reduced risk of disease/death, which would mean that the overall mortality rate of COVID-19 infections should start to go down, but there will still be transmission among people who have not received the vaccines and are not immune.

For that reason, we can’t just immediately stop taking COVID-19 precautions as soon as vaccines start to be rolled out. It will probably be of a gradual return to normalcy that will take place over the course of 2021, rather than an abrupt end to pandemic-mode.

How long will immunity from the vaccine last?

We don’t know yet, but current data suggest that some of the vaccines may induce greater antibody responses than actual infections in some people, particularly compared to asymptomatic or mild infections. Other data from the clinical trials have shown that immune responses to the vaccines last at least for a few months.

Since COVID immunity declines over time, it seems like it will probably not be one-and-done; you’ll probably eventually need a booster to retain high levels of immune protection. We will have to wait for longer follow-up data from the clinical trial participants to see when they start to be at risk of infection again to find out if/when a booster would be needed.

How many people would have to receive the COVID-19 vaccine to reach “herd immunity”?

This is somewhat tricky to answer, but the answer is that probably somewhere in the range of 60–80% of the population would have to be immune at the same time to reach the lower limit required for herd immunity. This is a moving target, though, particularly since we know that immunity wanes over time. For example, if 85% of the population chose to get the vaccine, but due to supply limitations, those 85% received them spread over the course of 12 months, it’s possible that some of the first people who got them would already have decreased immunity by the time the last people did. (This is purely theoretical, just meant to show why it’s hard to calculate an exact number of people who would need to be vaccinated to reach herd immunity).

One important point, though, is that this is not an all-or-nothing endeavor. Even if only 40% of the population is immune at one time, that is still going to slow down the rate of viral spread, even if it does not fully eliminate viral spread. Any incremental increase in immunity is a step in the right direction that will slow down spread.

One thing that is for sure is that it is not a good idea to try to just intentionally infect the entire population with COVID-19 to try to get to herd immunity. Even if you think that there is a 99.9% survival rate, you’re still proposing hundreds of thousands of deaths and that is not even considering the risk of long-term side effects in people who do survive. The vaccine is the safer way to move toward herd immunity, but our ability to get there will be rate-limited by 1) vaccine supply, and 2) peoples’ choices to get the vaccine or not.

Here is a good article from Nature discussing herd immunity and COVID

Prepare for a massive misunderstanding of correlation vs. causation.

I am actually quite concerned about this next point. We are about to experience a MAJOR problem stemming from a lack of understanding of the difference between correlation and causation.

Vaccine safety will continue to be monitored as vaccines are rolled out to the general public in order to assess for any true indications of safety concerns that may emerge from the data, but there will also be a lot of random medical events that are unrelated to the vaccines. Biostatisticians will have the tools and training required to analyze the data to pick apart what may or may not be related to the vaccines, but most of us will not those tools (or the necessary training).

If you were to bring 20 million people into the doctor’s office and give every single one of them a placebo injection of plain, harmless, salt water, then follow-up with them one month later, thousands of those patients would experience really bad medical events like heart attacks, newly diagnosed cancers, and death. Would those things be due to the injection of salt water? Probably not — these are events that just-so-happened to occur in the time following the doctor visit, and, in a large enough group of people, these things happen every single day of the year. Some of those theoretical 20 million people may have even had something like a heart attack within just a few hours after their salt water injection.

The reason why you run tightly controlled clinical trials is to test whether the group that received the “test” treatment had any increased rate of adverse events compared to the placebo group. In some cases, you can also compare to known rates of adverse events that occur in the general population.

As millions of COVID-19 vaccines are actually rolled out to the population, there are undoubtedly going to be situations where people who receive a COVID vaccine end up getting in a car accident later that afternoon, have a heart attack the next day, etc. For those of us without access to the massive databases collecting ongoing safety information, the difference between vaccine-related and -unrelated events will be very difficult to discern, since we don’t have an easy way to compare the overall rates among people who received the vaccine against population-wide trends prior to the vaccine. So, we will have to be on the lookout to try to avoid interpreting individual anecdotal reports with the same confidence as we interpret official statistical interpretations of the data.

Who sponsored this post?

No one sponsored this post, and I have received zero financial support from any vaccine producer, government agency, or anyone. I hold no stocks or options in any of the COVID-19 vaccine producers. I hope it is clear that none of this info is medical advice, and is intended to provide you with links to some more authoritative sources for these common questions. Several very kind people did buy me coffees to fuel my writing and researching endeavors, and to them, I would like to say: thank you! I hope you found this helpful in some way.

@dr.noc on Instagram and TikTok

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