On June 17, 2022, the Food and Drug Administration (FDA) issued an emergency authorization for the use of the Pfizer-BioNTech and Moderna COVID-19 vaccines in children older than 6 months. 1 The following day, Dr. Rochelle P. Walensky, director of the Centers for Disease Control and Prevention (CDC), announced that CDC would recommend that all children between the ages of 6 months and 5 years receive a COVID-19 vaccine. 2
Previously, children under 5 years old were ineligible to receive COVID-19 vaccines due to concerns about the effectiveness of the vaccines in that age group. In December 2021, Pfizer announced that the vaccine did not generate a sufficient immune response in children under 5 who received the vaccine as part of a clinical trial. 3 The participants were given two 3-microgram doses, and while no safety concerns were reported – adults typically receive 30-microgram doses – an immunogenicity analysis revealed that children under 5 developed a much lower immune response than cohorts of 16-25 year-old participants. Interestingly, only the 6-to-24-month population passed the threshold for “non-inferiority:” the vaccine was not worse than a control treatment in this cohort.
Following these results, Pfizer updated their study and administered third doses to children under 5, and the results from this trial were much more encouraging. Vaccine efficacy was established in 80.3% of the participants, as was a safety profile similar to that of a placebo. 4 Interestingly, the Moderna vaccine for children under 5 consists of two 25- microgram doses, but has only shown a 40-50% success rate in preventing COVID-19 infections. 5 Moderna has acknowledged this relatively low vaccine efficacy rate and will likely offer a booster shot to children in this age range in the future.
Despite the infrequency of COVID-related infections and deaths in children under 5 compared to adults, COVID-19 has impacted individuals in that age range. According to CDC data, children ages 6 months-4 years had more COVID-19 associated hospitalizations during the Omicron wave of late 2021-early 2022 than children of any other age. 6 Though children in the 6 month-4 year age range on average experience lower mortality and adverse health outcomes than older children, they were admitted to the ICU for COVID- 19 more often than older children. 6
COVID-19 can thus pose a serious health risk for children under 5, though unfortunately, it appears that vaccination rates for these children will likely lag behind the rates for adolescents and adults. Approximately 700,000 children in the US under 5 have received at least one dose of the COVID-19 vaccine, despite there being about 19 million eligible children in this age range. 7 In anticipation of the lack of demand (on occasion, for political reasons), several US states have ordered fewer COVID-19 vaccine doses for children under 5 than for other age groups. 8 Vaccination in older children has also stalled: in only 6 states have more than 50% of children 5-11 received one vaccine dose. 7 Public health workers are sympathetic to the concerns of parents that the vaccine in children is unnecessary or harmful, but are urging them to reconsider; hopefully, their efforts will result in increased vaccination in children under 5.