Moderna Pfizer Vaccine

mRNA and DNA

Messenger RNA (mRNA) vaccines (like Pfizer and Moderna) do not alter your DNA.

In fact, they lack all of the basic requirements necessary to alter DNA. In other words, it’s biologically impossible.

In order for a mRNA vaccine to alter someone’s DNA, several events would have to occur…

  1. mRNA would need to enter the cell nucleus, where DNA lives. However, mRNA do not have the “secret door code” (called nuclear access signal) that would allow it to enter. mRNA vaccines can’t get in.
  2. If the mRNA vaccine did get in (which it won’t), mRNA would have to be then converted to DNA. This would require a tool called “reverse transcriptase”, which the vaccine doesn’t have.
  3. Also, if it made it into the nucleus, mRNA would then to need to insert itself into the DNA. The mRNA would need a tool called “integrase” to do this, which the vaccine doesn’t have.

mRNA is found in all living cells. So, sorry to break it to you, but you already have mRNA within you. This is because our cells need instructions on how to function. The mRNA vaccines add a chapter to this instruction manual: “how to properly to fight the COVID19 virus”.

Some vaccines are being developed and tested to target DNA. And they are also safe (but I can explain at another time). Also viruses like HIV can integrate themselves into DNA, but this isn’t true of all viruses, and HIV can only do so with the help of special tools. None, of which, the COVID19 vaccines have.

Love, YLE

Data Sources:–faq/

Moderna Pfizer Vaccine Variant

Vaccines are made with mutations in mind

The Moderna and Pfizer vaccine induces something called a polyclonal response. Basically, the vaccine instructs the body to generate numerous shaped antibodies that can connect to many different parts of the virus (see picture). Those antibodies are diverse in shape and cover the whole waterfront of the spike protein.

A spike protein mutation here and there would still leave areas for the antibodies to attach. Mutations to those target sites raise the possibility that the vaccines would be less effective, not necessary that they won’t work at all. Mutations are likely a long way from making any vaccine useless. Scientists say it will probably take years.

However, if a random mutation did render a vaccine useless, the mRNA instructions are incredibly easy to change. This is the beauty of this type of vaccine. It’s like editing a Word document; just tweaking the code a little. And, the FDA wouldn’t need Phase I-III trials again. This is because the code isn’t changed enough to concern safety or efficacy. They would just need to see a study with a few dozen people that showed the new code produced satisfactory amounts of antibodies and protection against the mutated virus.

According to GISAID (a public genetic database of the virus) there’s about 12,000 known mutations for the COVID-19 virus. And the mutations in a few (UK, SA, Brazil, and Nigerian variants) look like they change some of the target sites, but certainly not all.

We are still very much hopeful for the effectiveness of the vaccines.

Love, YLE

Some data sources for more reading:
WHO 12,000:—5-january-2021

Antibodies Vaccine

Vaccine after COVID19 infection

If you’ve previously had COVID19, you still need the vaccine.

Let me repeat for the back to hear.

If you’ve previously had COVID19, you still need the vaccine. Even if you had a positive antibody test.

Studies have shown that ~10% of people who recovered from COVID19 have weak antibodies and they wean off after a while (it looks like about 90 days). When the antibodies wean off, you will get reinfected if you come in contact with the virus again. And you won’t have protection. (By the way, this is what’s causing the small rate of reinfections).

Unfortunately, we can’t accurately predict who those 10% of people are. The only thing we know is that typically mild infections don’t mount a strong or lasting immunity to the virus. The worse the first infection, the stronger the immune response will be.

So, because we don’t know whether you land in the 10% category, everyone needs a vaccine. Vaccines provide you with the “perfect formula” needed to have a strong antibody response so the virus doesn’t overwhelm your body. Everyone will be on the same playing field.

Strong “natural antibodies” (ie not from a vaccine) have shown to last up to 8 months. But that’s because these studies were only 8 months long. As I’ve mentioned many times before, we are expecting antibodies to last 1-2 years because that’s how long COVID’s cousins last (SARS & MERS). Not enough time has passed to know for sure. Also, we won’t know how long immunity produced by vaccination lasts until we have more data on how well the vaccines work. There no reason to believe, though, that “vaccine antibodies” act differently than strong “natural antibodies”.

If you currently have COVID19, you CAN wait up to 90 days for your vaccine. That’s because reinfection is incredibly rare before 90 days. But you CAN get it sooner. Pfizer clinical trials included people who did or did not have COVID-19 previously and some people got the virus during the study. These situations did not present any issues of concern. If you currently have active symptoms of COVID-19, the CDC recommends you wait to get vaccinated until you’ve recovered and met the criteria for ending isolation:

  • At least 10 days have passed since symptom onset AND
  • At least 24 hours have passed since resolution of fever without the use of fever-reducing medications AND
  • Other symptoms have improved.
  • And that’s mainly because we don’t want you infecting other people when you go get your vaccine.

Love, YLE

Data Source:
~10%: ; ;
Ending home isolation:
How long antibodies last:

Side Effects Vaccine

Vaccine and pregnancy/breastfeeding…

A really tough decision. Data is limited and theoretical risk must be weighed against the established benefits. This is what we have so far…

-Individuals who got pregnant during vaccine trials had no complications from the vaccine
-Pregnant, vaccinated rats did not have any adverse effects on female reproduction, fetal/embryonal development, or postnatal developmental.
-The vaccine mRNA will not reach the baby; it degrades too quickly
-The vaccine is not “live” or “dead” or anything in between, so you won’t get infected with COVID19
-Antibodies do not attack the placenta
-There is no plausible way how the vaccine would cause harm to a breastfed baby
-Pregnant individuals are at higher risk for COVID19 complications
-CDC, FDA, ACOG, and ABM all recommend vaccination for pregnant and breastfeeding individuals in particular

Long version:
Pregnant and breastfeeding patients were deliberately excluded in the first round of COVID19 vaccine clinical trials. This is normal practice (however lately it’s been strongly debated that we should include pregnant individuals as they have been dubbed “last therapeutic orphans.” The history of this topic is fascinating.) With that said, a number of individuals in these trials did get pregnant after they were enrolled in the study: 23 in the Pfizer trial and 13 in Moderna. None had complications from the vaccine.

Moderna also published their DART results. This is an animal study done before human trials begin. This is also normal practice (not just done for COVID19). Moderna injected pregnant rats with the vaccine. Rats did not have any adverse effects on female reproduction, fetal/embryonal development, or postnatal developmental. Pfizer is still working on their study and will publish soon.

The fundamental principles of how mRNA vaccines work are important to understand:
-These vaccines do not enter the nucleus and do not alter human DNA in vaccine recipients. As a result, mRNA vaccines cannot cause any genetic changes to mom or the baby
-mRNA is degraded quickly once it sends this message to your immune system. It won’t have enough time to get to the baby even if it wanted to.
-There is no live or weakened virus in the vaccine, so you cannot become infected from the vaccination itself. Vaccines that do include live or weakened virus (like MMR) are not given during pregnancy.
-Antibodies do not attack the placenta (regardless of the misinformation circulating the internet. check out my previous post about this)

In terms of breastfeeding, there is no plausible biological mechanism for how the vaccine would cause harm to a breastfed baby. We’ve seen small studies that COVID19 positive patients DID pass antibodies to their breastfed child. Antibody protection is one of the big benefits of breastfed milk. While we do not yet have data specific to maternal vaccination, information from other respiratory disease vaccinations suggests newborn protection is likely.

Although the absolute risk for severe COVID-19 is low, symptomatic pregnant patients with COVID-19 are at increased risk of ICU admission, need for mechanical ventilation and ventilatory support, and death. This is why pregnant individuals are being offered the vaccine in the first rounds of vaccinations.

With all of this in mind, the CDC and FDA have recommended vaccination for pregnant and breastfeeding individuals. Also (and I think more importantly):

  • American College of Obstetricians and Gynecologists (ACOG): “vaccines should not be withheld from pregnant or lactating individuals who otherwise meet criteria for vaccination.”
  • Academy of Breastfeeding Medicine does not recommend stopping breastfeeding for people who get the COVID-19 vaccine.

Have a discussion with your provider. If they don’t want to have a discussion, find another provider. Here are topics to discuss:

  1. Level of COVID-19 spread in your community;
  2. Whether you have any medical conditions that elevate your risk of COVID-19 complications;
  3. Your comfort level in taking the vaccine.

This is your decision. As a scientist (and mom), all I can do is provide you with the current state of evidence. I hope this helps. And congratulations on your baby!

Love, YLE

Previous post on fertility and vaccine:

Data Sources:
Pfizer report:
Moderna report:
UK vs US recommendations:
Antibodies in human milk:
Covid risks to pregnant individuals: ; ; ; ; ;


Vaccine hesitancy…

Vaccine hesitancy…

On Dec 30, a systematic review was published on vaccine hesitancy. The scientists basically pooled ALL articles on the topic of “COVID19 and vaccines acceptance” and summarized general trends or themes. For this study, the scientists pooled a total of 126 studies on this topic.

What did they find?

  • In the US, vaccine acceptance is declining (72% in April to 48% in Oct)
  • Countries with the highest rates of vaccine acceptance were China (91.3%), Brazil (85.36%), South Africa (81.58%), Denmark (80%), S Korea (79.8%) and the UK (79%)
  • Outside of the US, Russia had the lowest vaccine acceptance (54.9%), followed by France (58.9%)
  • People with lower income, no insurance, living in rural areas or larger households are less likely to get vaccinated
  • Most common reasons for hesitation: fear of side effects, safety, and effectiveness.
  • Lower acceptance of vaccines were due to: Belief that vaccines are unnecessary, inadequate information, unknown/short duration of immunity, and a general anti-vaccine stand
  • Confidence was boosted from doctor recommendations or positive opinions from family and friends

This data has been backed by anecdotal reports of only ~50% of healthcare workers wanting their vaccine. In fact, many hospitals ordered too many vaccines. We need at least 65% of people vaccinated to reach herd immunity.

My scientific opinion: Vaccine hesitancy isn’t as sexy as a mutation, but I would (and am) much more worried about this than the SA or UK variant. And you should be too. Vaccine hesitancy is an imminent threat to this pandemic.

If you’re vaccine hesitant and there’s a topic that I haven’t already covered which would help you make a data-informed decision, please comment below. I’ll try and do my best to post about it in the coming weeks. These are the topics I’ve covered thus far: side effects, adverse events, efficacy, types of vaccines (Moderna, Pfizer, Johnson&Johnson, AstraZeneca, Novavax, Sputnik), fertility, antibody response, long term effects, and me getting the vaccine. (If you missed any of these, search my blog for a key word or press on the category “vaccines”).

If you’re vaccine confident and happen to come across someone who’s hesitant or resistant, here are some tips on what to say (and not to say). Yes, this includes social media. First and foremost, be kind. See Figure. We are all needed in this vaccine campaign.

Love, YLE

Data Source:
Systematic Review:
Language that works link:


Sputnik V

Sputnik V (yes, named after the first satellite) vaccine…

This vaccine (also called Gam-COVID-Vac) was developed by Russia’s Ministry of Health (Gamaleya Research Institute). The vaccine is 2 doses, 3 weeks apart. It’s an adenovirus (like AstraZeneca) that needs to be stored in a freezer. The innovative aspect of this vaccine is that scientists combined two adenoviruses instead of using just one. By doing this, they hope the virus can’t mutate to outsmart the vaccine.

Here’s the vaccine’s timeline:

June: Phase I/II trials launched

Aug 11: Putin announced they conditionally approved the vaccine. Other countries do this too. The motive was political, however, as it’s now considered the “first registered vaccine” in the pandemic. Which, as you can imagine, is controversial.

Sept 4: Results from Phase I/II were published in the Lancet (a very well-respected journal). In short, among 76 people aged 18-60, the vaccine was safe with most adverse events being mild and no serious adverse events reported. The vaccine also yielded antibodies.

Oct 17: Phase III began. Participants were recruited in Belarus, UAE, Venezuela, and India.

Nov 11: Russia sparked significant controversy (again) because, after releasing partial Phase III data, they began offering the vaccine. The partial data was based on 20 cases of COVID19, where scientists estimated a vaccine efficacy of 92%.

Dec 14: Phase III trial reached 22,714 participants (17,032 in the vaccine group and 5,682 in the placebo). After two months, 78 cases of COVID19 popped up (16 in the vaccine group and 62 in the placebo group). This equates to an efficacy rate of 91.4%. Out of the 78 COVID19 cases, 20 cases were severe and all were in the placebo group. Results have not been peer-reviewed yet.

Dec 29: Belarus and Argentina approved for emergency use.

An interesting development: Sputnik just reached a deal with AstraZeneca. The motivation is to try and increase AstraZeneca’s efficacy by combining the two vaccines. They are both adnoviruses, so this is possible to do. However, it has just never been done before. It’s unprecedented. Nonetheless, they need to start from the beginning (Phase I). AstraZeneca just registered for the trial.

My opinion: Look, I know this is a Russian vaccine. And, yes, they chose a really poor vaccine name. Their urgency to be label their vaccine the “first vaccine approved” was cause for concern. And approving a vaccine, before Phase III is complete, is also cause for concern. But, after reading the science, I see no reason to doubt the results. The Lancet results are solid. And the Phase III results are on par with what we have seen with the other vaccines. We are anxiously waiting the peer-reviewed science, but we also are for AstraZeneca. Also, Russia is paying for their poor initial decisions, as there is significant vaccine hesitancy within the country. But this is a global pandemic with literally billions of people infected and millions of people dying. It’s important that we give all vaccines, especially those that are easy to store and distribute to reach the most vulnerable of populations, a fighting chance. Even if they do come from Russia.

Love, YLE

Data Sources:


Phase III press release:

AstraZeneca Moderna Pfizer Vaccine

Delayed Second Dose

People who got their first Pfizer and Moderna vaccine are expected to get their second dose 21 and 28 days later. The UK just approved AstraZeneca, of which people got their second dose 28 days later in clinical trials.

However, yesterday the UK made waves by announcing that they are prioritizing first doses. In other words, people won’t get their second dose of AstraZeneca or Pfizer until up to 3 months after their first dose. This is a bold approach… give as many people their first dose as fast as possible (rather than providing two doses to fewer people). Some places in Canada have been doing this and Belgium is considering it too.

Does timing of the second dose matter? This question has sparked quite the scientific debate.

On one hand, this could be a brilliant decision. Especially in a country where transmission is out of control due to a new variant. This decision could result in less deaths. Biologically (and historically) getting a vaccine a day or week late doesn’t matter much. The immune system usually doesn’t need that much precision. And sometimes the longer between doses, the better efficacy. But 3 months later? Not sure.

On the other hand, this could be a regrettable decision. During a pandemic with significant transmission of a disease, getting a vaccine exactly as it had been studied is important because: 1) People are much better off being fully protected. For example, in the Pfizer trial, the level of protection increased dramatically (52% to 95%) after the second dose; 2) The second dose typically provides longer-lasting immunity than the single dose; and, 3) Dr. Paul Bieniasz (Rockefeller biologist that studies the evaluation of viruses) said that this could cause partial antibody resistance among a population that is semi-immunized. “If I were designing a vaccine-resistant [COVID19 virus], I’d do what they are doing in the UK”. This is an experiment in viral evolution during the middle of a pandemic.

So, in short, the vaccine studies weren’t designed for a delayed dose, so we really don’t know the implications. AstraZeneca also hasn’t released their full data report, even though the regulators had a copy this week. So we can’t really parse out the data to make more accurate hypotheses. Word on the street is that some people had their second dose in the AstraZeneca trial much later than 28 days, but I have yet to see that data.

We’ll just have to see how this goes…

Love, YLE

Side Effects Vaccine

Adverse Events Update 12/28/2020

As of December 28th, 2.13 million Americans received their first dose of the COVID19 vaccine; 11.45 million doses have been shipped to US providers.

Among the 2.13 million Americans, there have been only 353 people (that’s 0.017%) who reported an adverse event to the CDC.

Among the 353 people that experienced adverse events…

• The vast majority have mirrored mild-to-moderate reactions in clinical trials (see first figure; these are not mutually exclusive)

• Only 8 of these events are classified as “serious” (see second figure)

• Of the 8, 4 people were hospitalized

• 0 have resulted in death

• 73% of the events occurred in young adults aged 18-49

• 2 events were severe allergic reactions (anaphylactic shock)

Adverse events for COVID19 vaccinations (and all vaccinations by the way) are tracked and reported within the CDC Vaccine Adverse Event Reporting System (VAERS). This information is ALL public and you can play around with tables and charts here: This system even allows you to read the physician notes on what exactly happened with each patient. It’s incredibly transparent.

Keep in mind that not every system is perfect; there are some limitations to VAERS. Healthcare providers, vaccine manufacturers, and the public can submit reports to VAERS. While very important in monitoring vaccine safety, VAERS reports alone cannot be used to determine if a vaccine caused or contributed to an adverse event or illness. The reports may contain information that is incomplete, inaccurate, coincidental, or unverifiable. Most reports to VAERS are voluntary, which means they are subject to biases. This creates specific limitations on how the data can be used scientifically. Data from VAERS reports should always be interpreted with these limitations in mind.

Love, YLE

Data Source:

Graphs: By yours truly

Texas update Vaccine

Phase 1B opened in Texas

Texans….Phase 1B has opened.

So, if you’re in this category, you can now get the COVID-19 vaccine (depending on local availability):

• People 65 years of age and older

• People 16 years of age and older with at least one chronic medical condition, such as but not limited to:

• Cancer• Chronic kidney disease• COPD (chronic obstructive pulmonary disease)• Heart conditions, such as heart failure, coronary artery disease or cardiomyopathies• Solid organ transplantation• Obesity and severe obesity (body mass index of 30 kg/m2 or higher)• Pregnancy• Sickle cell disease• Type 2 diabetes mellitus

Here is the map of vaccine providers:…/webappvi…/index.html…

This week 380,000 doses (175,100 Moderna and 81,900 Pfizer) were sent to Texas providers in 199 counties. This obviously doesn’t cover every Texan in Phase 1B. Be patient. Some providers may not have vaccines available yet. Vaccine supply is limited but providers receive more vaccines each week.

Update: As of 4pm today, 204,463 Texans have gotten their first dose!

Love, YLE

For more, check out the DSHS website here:…/immunize/vaccine.aspx…

Novavax Vaccine

Novavax Vaccine

Alright, now on to Novavax…

Novavax is a small company based in Maryland and has never brought a vaccine to market. This company has a fascinating rollercoaster history; I highly recommend googling over coffee.

Novavax is using a different vaccine formula than Moderna, Pfizer, AstraZeneca, and Janssen. The Novavax vaccine contains a cornavirus protein that prompts the immune system. Scientists combined this protein with an immune-boosting compound derived from the soapbark tree. They tried doing it without this adjuvant but the vaccine didn’t work as well. Anyways, this type of vaccine has a much longer track record than the newer approaches.

The exciting (and innovative) aspect of this vaccine is that Novavax found a way to make this vaccine in moth cells (rather than mammal cells). The moth cells basically become little factories that pump out coronavirus proteins. This allows Novavax to manufacture the vaccine much quicker than others, which is obviously a big plus in the time sensitive pandemic.

The Novavax vaccine has gone through animal and small human trials so far. In animal studies, the Novavax vaccine provided stronger protection for monkeys than have other coronavirus vaccines. This isn’t surprising though, as other scientists predicted (and published) that the protein-based vaccine would be highly effective.

In August, Novavax published promising preliminary results: 56 volunteers produced a high level of antibodies against the virus without any dangerous side effects. Then, in September, Novavax started human Phase III trials in Britain among 15,000 people. The results from this trial should be ready early 2021. Novavax said that over 25% of participants in this trial are over the age of 65, with a lot of participants also having underlying medical conditions.

Yesterday, Phase III started in the US and Mexico. They plan on enrolling 30,000 people at 115 sites. It was supposed to start earlier (October), but Novavax ran into commercial manufacturing scale-up problems.

Love, YLE

PS After seeing some concerning comments yesterday, I want to make it very clear that I have no conflicts of interest with any of these vaccine sponsors. Although it would be nice to be paid for this 😉 (half joking). I’m cheering for all the vaccines to make it to the finish line, but I think education and transparency is equally as important for the community.


Early results:

Novavax History:…/coronavirus-vaccine-novavax…