Ask a Virologist
or, answering reader questions on COVID vaccines, masking in schools, and more
As we enter our third year of the pandemic, COVID remains top of mind for most parents. Omicron continues to spread, daycare and school closures are still common, and vaccines may soon become available for very young kids. Though we know so much more than we did in March 2020, there is still confusion and conflicting information, and parents are left feeling frustrated.
COVID currently dominates many of the conversations that I have with the working parents I coach. They certainly find value in processing the impact of the pandemic on their lives, but sometimes they just want clear answers and help interpreting complex data. Luckily, I know a guy…
Craig Wilen is a physician, scientist, and Assistant Professor at Yale who runs a lab focused on viral pathogenesis and immunity. He also happens to be my husband 😉 Craig is a virologist and clinical pathologist who received his MD/PhD from the University of Pennsylvania. He has authored over 30 papers on SARS-CoV-2, and he graciously agreed to answer questions submitted by readers through my Instagram (@drjessicawilen) and personal Facebook page.
What is the difference between mRNA vaccines and other childhood vaccines?
mRNA vaccines are a new type of vaccine based on an old idea. All vaccines are based on the same principle: a vaccine must present an immunogen (i.e., part of a virus or bacteria) to the immune system to trick the immune system into making antibodies and/or T cell responses against that immunogen.
There are different ways to present immunogens to the immune system. The oldest method is to use live attenuated or weakened viruses/bacteria that can replicate in a person but cause limited to mild disease. This is the basis for many vaccines including the smallpox vaccine, the oral polio vaccine, and the flu mist nasal vaccine, amongst others. A second method is to use heat-killed or chemically inactivated virus or bacteria as an immunogen. This is the basis for the intramuscular polio vaccine and seasonal flu vaccines. A third method is to make purified recombinant proteins or immunogens in the absence of any pathogen. These vaccines are called “subunit vaccines” and examples include the pertussis and hepatitis B vaccines.
mRNA vaccines function similarly to a subunit vaccine, but perform better. In the case of the mRNA vaccines, the viral subunit is the coronavirus spike protein. The mRNA in the vaccine encodes instructions for the body’s own cells to make the spike protein. Think of it this way: DNA is the blueprint for a building and mRNA is the contractor who helps turn the blueprints into instructions for the construction workers (i.e., the proteins).
I thought data showed that the Pfizer vaccine wasn't effective for kids 2-4. Why would it be approved if it doesn't work?
The Pfizer mRNA vaccine was originally tested as a two-dose regimen in kids aged 6 months through 4 years old. This original study used 3 micrograms of vaccine per dose. In contrast, 5- to 11-year-olds receive 10 micrograms per dose, and people 12 and older get 30 micrograms per dose. The two-dose regimen did not produce the same level of antibodies in 2-4 years old that it did in 6 month to 2-year-olds and older populations. This suggests that the vaccine, as tested, may not provide optimal protection in 2- to 4-year-olds. In response to the low antibody levels in 2- to 4-year-olds in the initial study, a third 3 microgram shot was added two months after the second dose. It is expected that this third shot will boost antibody levels, which correlate with protection, and thus would suggest the vaccine prevents disease in children under 5.
The two-dose clinical trial did not look at the ability of the vaccine to prevent infection or disease because the number of study participants was too low. Instead, it used antibody levels as a correlate for disease protection; however, it’s important to understand that antibodies are only half of the adaptive immune system. T cells make up the other half and data about T cell levels have not been released yet. Also, even low levels of antibodies are likely to confer some protection.
The bottom line is that we do not know for certain what level of protection the vaccine will provide to young kids. The current clinical trials were not designed to test this, so we have to extrapolate what we know about vaccine efficacy in older kids and adults. It should be noted that when the vaccine was approved in kids 5 and older, we also did not have efficacy data (we only had the antibody data, which suggested it would be efficacious). The alternative to not authorizing the vaccine in young kids is that they will almost certainly get COVID. As the risks of vaccination are extremely low, the benefits almost certainly would outweigh the small risks. I suspect recommendations regarding the best dosing interval and dose amount may change in little kids over time as new data emerges.
Can you explain the approval process (Are these vaccines still in clinical trials? What phase? Are they fully approved? How does safety data compare to other FDA-approved vaccines?)
The Pfizer mRNA vaccine is fully approved for use in people 16 and older. It is being used under emergency use authorization for 5- to 16-year-olds. It is currently in phase 2-3 trials for kids 6 months through 4 years old. Clinical trials for the Pfizer vaccine are furthest along, but Moderna also has ongoing clinical trials in children (the Moderna vaccine just received full FDA approval for individuals 18+ earlier this week). The Pfizer mRNA safety data is excellent in young children, with even better side effect profiles in kids than adults. However, only several thousand young kids have been tested in clinical trials so very rare side effects may not be known yet. Based on everything we know from older kids and adults, side effects are anticipated to be very minimal in younger kids.
What side effects should I look out for?
Side effects in kids under 5 are expected to be similar to, and likely milder than, what we see in older kids and adults. The most common side effects are fever and inflammation at the injection site. Temporary and mild inflammation of the heart, called myocarditis, was seen in ~1:100,000 adolescents and even less commonly in 5-11 year olds. The reasons for this age-related difference are not known, but based on this data, it is expected vaccine-induced myocarditis will likely occur even less frequently in the youngest age group. The good news is that vaccine-induced myocarditis is self-limiting and less common than myocarditis caused by actual COVID-19 infection.
Any idea when Moderna will release their vaccine for 0-4?
Trial data is expected in March 2022. Assuming the data is promising, it should be reviewed and authorized several weeks thereafter.
Should kids who have tested positive for COVID twice in the last year still get vaccinated?
Yes. Previous infection confers decent but not optimal immunity, which is why you can get COVID multiple times. Infection-induced immunity can be boosted by vaccination after infection. While the pediatric clinical trials are not powered to test this directly, vaccination after infection in adults increases antibody levels and confers increased protection from severe disease. The same is expected to be true in children although it will not be formally tested in the current trials. There are no known additional risks or side effects if you get vaccinated after previous infection.
If my child will be 4.5 when shots are available, do we consider waiting until she's 5 for the bigger dose?
No. Get her vaccinated as soon as possible. Additional boosters may be indicated, and data will quickly emerge showing whether boosters or higher doses are needed in kids as they age. Once the vaccines are authorized in kids, this data will rapidly accumulate outside of clinical trials.
I was vaccinated when I was pregnant and am currently breastfeeding, so presumably my son has some antibodies. Does he still need a vaccine?
Yes. Though your son does have some passive antibodies, he is not making his own antibodies and thus does not have optimal protection. Breastfeeding also does not provide T cell-mediated immunity to your son. T cells against the virus are another important part of the immune response, and they can only be elicited by infection or vaccination. Vaccination will cause your son to generate his own antibodies and T cells against SARS-CoV-2 and these vaccine induced antibodies and T cells are expected to last for decades and provide some degree of long-term protection.
I've heard that an Omicron-specific vaccine is being developed. Should my family get this?
Omicron mRNA vaccines are in development, but we do not know if they are similar or better than the original mRNA vaccines. It’s possible an Omicron-specific mRNA vaccine will provide better protection, but we don’t have any evidence in support or against this. The good news is that a third dose (booster) of the original mRNA vaccine does provide great protection against hospitalization and death from the Omicron variant, so protection is available NOW for people 12 and older. Also, Omicron is almost certainly not the last variant of concern that will emerge. It’s very likely the next variant may replace Omicron and we could be talking about Pi or Sigma or Omega in 6 or 12 months.
My nanny is vaccinated, but she won't vaccinate her kids. How concerned should I be about this?
Your nanny is more likely to get COVID given that she lives with unvaccinated kids, so this does marginally increase your family’s risk. It’s important your nanny is boosted because this third shot will significantly reduce her chance of transmitting the virus to your family.
I've been seeing a lot of petitions against masking kids at school. What do you make of this? When will it be safe for kids to stop masking?
Masks can be annoying, but they are effective at reducing infection and transmission. There have not been randomized control trials in children, in schools, or in the US, so the best evidence is from a randomized control trial in Bangladesh. By using multiple strategies to increase community mask use from about 10% to about 40%, they were able to achieve an 11% reduction in symptomatic disease.
There is no absolute threshold when masking can or should be stopped. It’s a balance between risks and benefits. Right now, in my opinion, the benefits outweigh the risks, especially given the low pediatric vaccination rates in many parts of the country. As infection incidence lowers and vaccine rates increase, masking can begin to be relaxed. Adding COVID vaccines to the long list of already required vaccines for school children would go a long way towards this goal.
What are your thoughts on the need for 10-day quarantines post-exposure that many daycares are still using?
I think 10 days is overly conservative based on how long most people remain infectious. The data also suggests that 5 days is too liberal as a large minority of people still shed infectious virus at day 5. Personally, I think the best approach is “test to stay” which entails daily testing of exposed students. If they test negative, they go to school; if they are positive, they stay home. This keeps kids in school and is comparably effective to school closures at reducing transmission. The only limitation in the test to stay approach is that testing is not always available, but this is improving.
What guidance should I follow for playdates?
This is dependent on your risk tolerance and the perceived benefits of playdates to your family. For our family, we plan to resume indoor playdates with other asymptomatic and fully vaccinated families once infection levels come back down to pre-Omicron levels. We also plan to have rapid tests available and use them liberally before playdates when case counts are high or if we think we had a COVID exposure.
READ – CONNECT – REFLECT
You’re busy, I get it. Each week I provide a digest of important articles to read, new ways to connect with the people in your life, and a self-reflection question. Enjoy!
Let’s make sensitive the new strong (Marie Claire). I love everything about this article. “When boys exhibit qualities stereotypically reserved for girls—sensitivity, care, compassion—they are often undervalued or, worse, mocked. Boys who show emotion other than strength could face ridicule. It’s past time that we all learn to embrace, and even celebrate, these so-called ‘feminine’ attributes.” (Side note: these attributes are key components of emotional intelligent, and research unequivocally shows the values of these skills in the workplace.)
Child care workers are vanishing and it's hurting the entire economy (CNN). Child care workers are leaving their jobs for higher paying roles and the impact on both individual families and the larger economy is going to be devastating.
How to make sense of our COVID losses, big and small (New York Times). A beautiful essay on making sense of all that we’ve lost during these pandemic years. “There’s no pure form of any significant event in our lives, no single emotion that solely and accurately represents love, or grief, or pandemic. Even at the extremity of experience, life is always busy being many things at once — exhausting and restorative, tedious and exciting, solemn and comic, devastating and fulfilling.”
School closings are more complicated for parents of children with disabilities (The 19th). Remote schooling has been disproportionately challenging for children with disabilities and their families, who feel that schools have not done enough to accommodate their unique needs.
Four ways to fix performance reviews for caregivers (TIME). A useful article for anyone who manages, or is responsible for evaluating the performance of, working parents.
Art projects are what kept my kids and me (relatively) sane in the early days of the pandemic. I often turned to Meri Cherry, the owner of an art studio in LA, for inspiration. Her “process art” approach emphasizes the process of making art instead of the final product, which is especially helpful for perfectionist kids. Her instagram and blog are full of ideas to engage kids in fun art activities. Check out some of her Valentine’s Day crafts to work on as a family.
How can you better apply your greatest strengths?
I want to cover what’s important to YOU. I welcome reader input in deciding what and who to write about. Email me at firstname.lastname@example.org and put “newsletter idea” in the subject.
I also offer executive coaching and organizational consulting focused on the unique needs of working parents. To learn more visit Jessica Wilen Coaching LLC