The views and opinions expressed here are those of the authors and do not necessarily reflect the position of either Johns Hopkins University and Medicine or the University of Washington.
Children are not yet being vaccinated against Covid-19. Why? Although adults at highest risk of exposure and severe disease should be prioritized for vaccination, there are several reasons children and adolescents should also be vaccinated against Covid-19 when sufficient vaccine doses become available. First, although children and adolescents are much less likely to require hospitalization and die from Covid-19 compared to older adults, children can get seriously ill. More than 10,000 children have been hospitalized with Covid-19 in the United States and more than three hundred children have died. Of particular concern is a rare but serious complication of Covid-19 in children called Multisystem Inflammatory Syndrome in Children (MIS-C). The precise cause of MIS-C is not yet known but it results in chronic inflammation that can itself lead to death or long-term complications. Second, older children and adolescents can be important transmitters of SARS-CoV-2 in communities, spreading the virus to parents, grandparents, and other adults. Although we need to learn more about the impact of Covid-19 vaccines on transmission of SARS-CoV-2, emerging evidence suggests vaccination is likely to reduce transmission. Children make up nearly one-quarter of the population in the United States and we may not be able to significantly reduce community transmission if children and adolescents are not vaccinated. Lastly, getting children back to school, team sports, band practice, and regular social events is a priority. Although schools can and should be opened with strict adherence to public health measures well before children are vaccinated – and teachers should be prioritized for vaccination – vaccinating children may be an additional way to reduce virus transmission in schools.
So why are we not yet vaccinating children and adolescents? The Pfizer mRNA vaccine received Emergency Use Authorization from the U.S. Food and Drug Administration for people 16 years and older and the Moderna mRNA vaccine received authorization for persons 18 years and older based on participant eligibility in the large phase 3 trials. As is typical for clinical trials, studies are first done in adults. This was particularly important for Covid-19 as most of the severe disease and deaths were in older adults. Then, after the safety and efficacy of a vaccine are demonstrated in adults, additional studies are done in younger and younger groups of adolescents and children in a step-wise manner. These studies are frequently not as large as the studies in adults but are important to assess vaccine safety and immune responses in younger age groups. We now have a lot of data confirming the safety and efficacy of the Pfizer and Moderna vaccines in older adolescents and adults but further studies are particularly important in very young children as their immune systems are still developing; the vaccine dose or schedule may need to be adjusted to be appropriate to their smaller body size and different metabolism. Vaccine side effects may also be different in children and we will need to know the impact of vaccination on MIS-C.
So where are we in getting Covid-19 vaccines to children? While vaccine doses are in short supply, children are unlikely to be in a top priority group to receive the vaccine because they generally do not develop severe Covid-19. But progress is being made in evaluating Covid-19 vaccines in children. Pfizer has completed enrollment of 2,259 children and adolescents 12 to 15 years of age in its study of vaccine safety and immunogenicity that began in October 2020, and Moderna is enrolling up to 3,000 children and adolescents 12 to 17 years of age. Results of these studies should be available this summer, hopefully leading to Emergency Use Authorizations or full vaccine licensure for these age groups. However, additional studies will be needed in children younger than 12 years of age before Covid-19 vaccines will be available to them. It is important that these studies are done carefully and properly to ensure that the vaccines are safe and induce a good immune response in these younger children. Full results from these studies in younger children may not be ready until 2022. Several other vaccine manufacturers, including AstraZeneca, Johnson & Johnson, and Novavax, also plan to evaluate their vaccines in children and adolescents but have not yet started enrolling in the United States.
Building trust and confidence in Covid-19 vaccines for children is critical as up to one third of parents in the United States have stated they do not plan to vaccinate their children, while others can’t wait to have the vaccines for their children. Trials that evaluate these vaccines appropriately and show them to be safe and effective in children will go a long way in convincing more parents to vaccinate their kids when vaccines become available for them. Most importantly, this will help protect children, may protect the community at large, and will help us put the pandemic behind us.