Behaviors National changes Side Effects Variant

Quick update…

Several COVID19 developments popped up in the past 24 hours. Here’s my attempt to keep you up to speed…

-Data are stabilizing and we are starting to see the impact of the holidays. For the second day in a row the United States had more than 4,000 deaths per DAY. This is about what we, epidemiologists, expected because 22 days ago there were 239,795 daily cases. Today, 131,889 people are hospitalized and 7,900 people are on ventilators. We are hitting new records across every metric.

-There is NO scientific evidence of a new US variant (this is different than the UK or SA variant). This misinformation stemmed from a document circulated yesterday that speculated the increase in winter cases (compare to summer) must be due to a new variant. In Nov and Dec, 5,700 samples were collected and analyzed by the CDC and there is no evidence of this. However, the more this thing spreads, the more opportunity this virus has to mutate. Can we agree to start wearing masks and stop seeing friends?

-The Biden administration announced that they will not withhold the second dose. This is still a highly debated topic in public health (maybe the most debated since the pandemic began). My scientific opinion: Supply isn’t our issue right now; capacity and logistics are. As of this morning 22.1 million vaccines have been sent off; only 6.68 million Americans received their first dose. Yes, some of this discrepancy may be due to reporting lags, but this doesn’t explain it all. Our federal priorities should be setting up vaccine surveillance, setting up mass vaccination sites, and clear, consistent communication. Way too many people are in the dark. Now, if we get off the ground from this rocky start, then we can talk about the second dose.

-Every Friday the CDC Vaccine Adverse Event Reporting System (VAERS) is updated. The more people that get vaccinated, the closer we get to the “true” rate of adverse events. 6.68 million doses of the vaccine have been distributed and 3,907 adverse events have been reported to VAERS. The most common symptom is headache, nausea, and pain. 30 people/physicians reported anaphylactic reactions. On Jan 6, CDC published a report describing 21 of these cases in 1.89 million doses. Of which, 71% occurred within 15 minutes of vaccination. There are limitations to VAERS data (which I’ve posted about before).

Okay, I think that’s it for now.

Love, YLE

Data Sources:
Graph 1: Covid Tracking Project
Graph 2: Made by yours truly with VAERS data
Vaccine tracker:
CDC report:

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: ; ; ; ; ;

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