Over the past two weeks, the Food and Drug Administration’s advisory panel discussed Covid vaccines for infants and toddlers. The FDA voted unanimously (21-0) to authorize the use of the Pfizer and Moderna mRNA vaccines, and the CDC affirmed this vote with a recommendation supporting vaccination for all children ages 6 months and older.
- Moderna: ages 6 months through 5 years 25 mcg; ages 6 years through 11 years 50 mcg; and ages 12 through 17 100 mcg.
- Pfizer: ages 6 months through 4 years 3 mcg; ages 5 years through 11 years 10 mcg; and ages 12 through 17 30 mcg.
Many parents waited anxiously over a year-and-a-half for this news. The pediatric vaccines were found to induce a strong antibody response comparable to young adults when given as a two- or three-dose series. However, uncertainty remains regarding the degree of protection against hospitalization because only one hospitalization occurred in the trial. The child was a vaccine recipient infected with another common respiratory virus (human parainfluenza 3) at the same time. Thus, it is difficult to estimate specific protection against serious illness due to Covid until more data are gathered.
Remaining questions on Covid vaccines for kids
The clinical trials were able to show data on immunogenicity—how well the vaccines promote an antibody response—but were not able to show clear evidence of protection against infection or severe disease. The study groups were simply too small, cases too infrequent, and follow-up too short to mount commanding statistical evidence of effectiveness. The committee members considered the “totality of scientific evidence available” when considering their vote to authorize the vaccines for use in infants and children. The interim recommendation will be updated as more data is collected.
A large study is being conducted to follow real-world outcomes, but one of the challenges is that most children have already been infected with SARS-CoV-2, which provides substantial protection against both infection and serious illness. Against Omicron, prior infection offered 56% protection against a reinfection and 88% protection against serious disease over a median of 304 days after prior infection. The degree to which vaccination on top of natural immunity enhances protection in young children will be an important question to answer given their already low risk of serious illness.
Antibodies are not the only answer
Although antibodies naturally wane quickly and breakthrough infections are common, vaccination has provided durable protection against severe disease. How is this possible despite the shifting cast of variants?
The original spike protein used in the vaccines triggers a strong antibody response. Over time, the immune system matures by creating additional antibody “options” which can respond to variants even though they look a bit different than the original spike. The ability of these antibodies to neutralize new variants is lower, resulting in new waves of infection, however, other components of the immune system (T cells) play a vital role in preventing progression to serious disease. Even after antibodies wane, T cells remain on patrol to kill infected cells, preventing the virus from using the cell’s machinery to replicate. While variants may be able to evade the grip of antibodies, T cells are able to preserve about 80% of their ability to recognize new variants compared to the original virus. Thus, a focus on antibodies does not account for the full capacity of the immune system to fight infection.
Recovering from SARS-CoV-2 infection also triggers antibodies to the spike protein plus at least two dozen other viral proteins, and induces T and B cell memory. Because the virus enters through the airways instead of an injection into the arm, the mucus membranes are lined with special antibodies which can help prevent reinfection at the point of entry (called “mucosal immunity”). For this reason, people who have recovered from SARS-CoV-2 infection have very broad protection.
Shared decision-making important
Although the vaccine is eagerly sought by approximately 1 in 5 parents, perhaps you are hesitant about vaccination due to uncertainty regarding safety and necessity. It is important that your clinician offer a balanced discussion of risks and benefits which avoids overly positive and simplistic messaging. Your child’s unique health condition, and that of the household, should be considered.
At the end of the day-long FDA meeting, H. Cody Meissner MD, Chief of Pediatric Infectious Diseases at Tufts University School of Medicine offered the following closing remarks: “The vaccine should be available for children with well-recognized risk factors. It should not be mandated, that would not be appropriate, but for those families who really want to vaccinate their children and for those children who do fall into high-risk categories, the vaccine should be available.”
Help for hesitant parents
While you may not be ready to vaccinate your child against Covid today, consider two steps in the interim. First, schedule an appointment to follow up on any new findings in a couple months. The CDC and FDA will continue monitoring safety data using a variety of surveillance systems to detect rare adverse events, such as vaccine-induced heart inflammation (myocarditis). Additional studies will review the coadministration of the Covid vaccines with other routine pediatric vaccines, and last week the FDA approved (19-2) moving forward with developing booster vaccines which include an Omicron variant.
Second, remember that routine childhood vaccination against 20 diseases prevents 3.5-5 million deaths worldwide. In the US, the CDC monitors outbreaks of vaccine-preventable diseases, such as measles, which is included in the measles-mumps-rubella vaccine (MMR). When vaccine coverage is disrupted, such as by clinic closures, highly contagious viruses can resurface. A 2017 outbreak in Minnesota was contained by swiftly offering vaccination as depicted in the graph below. Keeping children up to date on all their routine immunizations can reduce their overall risk of serious illness due to the target disease, and research suggests that immunization also provides non-specific benefits against other diseases as well. Consider scheduling a well-child appointment to review other needed vaccines while thinking about Covid vaccination for your children.