The Centers for Disease Control and Prevention (CDC) followed up on the recent report that had questioned the efficacy of the Pfizer vaccine in 5-11 year olds. They found two doses of Pfizer-BioNTech vaccine provided protection against COVID-19 in persons aged 12–17 years during Delta predominance, but data during Omicron predominance and among children aged 5–11 years are lacking.
Two doses protect against COVID-19–associated emergency department and urgent care encounters among children and adolescents. However, vaccine effectiveness (VE) was lower during Omicron predominance and decreased with time since vaccination; a booster dose restored VE to 81% among adolescents aged 16–17 years. Overall, 2-dose VE against COVID-19–associated hospitalization was 73%–94%.
All eligible children and adolescents should remain up to date with recommended COVID-19 vaccinations, including a booster dose for those aged 12–17 years.
The efficacy of the BNT162b2 (Pfizer-BioNTech) vaccine against laboratory-confirmed COVID-19 exceeded 90% in clinical trials that included children and adolescents aged 5–11, 12–15, and 16–17 years.
Limited real-world data on 2-dose mRNA vaccine effectiveness (VE) in persons aged 12–17 years (referred to as adolescents in this report) have also indicated high levels of protection against SARS-CoV-2 (the virus that causes COVID-19) infection and COVID-19–associated hospitalization; however, data on VE against the SARS-CoV-2 B.1.1.529 (Omicron) variant and duration of protection are limited.
Pfizer-BioNTech VE data are not available for children aged 5–11 years. In partnership with CDC, the VISION Network examined 39,217 emergency department (ED) and urgent care (UC) encounters and 1,699 hospitalizations† among persons aged 5–17 years with COVID-19–like illness across 10 states during April 9, 2021–January 29, 2022, to estimate VE using a case-control test-negative design. Among children aged 5–11 years, VE against laboratory-confirmed COVID-19–associated ED and UC encounters 14–67 days after dose 2 (the longest interval after dose 2 in this age group) was 46%.
Among adolescents aged 12–15 and 16–17 years, VE 14–149 days after dose 2 was 83% and 76%, respectively; VE ≥150 days after dose 2 was 38% and 46%, respectively. Among adolescents aged 16–17 years, VE increased to 86% ≥7 days after dose 3 (booster dose). VE against COVID-19–associated ED and UC encounters was substantially lower during the Omicron predominant period than the B.1.617.2 (Delta) predominant period among adolescents aged 12–17 years, with no significant protection ≥150 days after dose 2 during Omicron predominance.
However, in adolescents aged 16–17 years, VE during the Omicron predominant period increased to 81% ≥7 days after a third booster dose. During the full study period, including pre-Delta, Delta, and Omicron predominant periods, VE against laboratory-confirmed COVID-19–associated hospitalization among children aged 5–11 years was 74% 14–67 days after dose 2, with wide CIs that included zero. Among adolescents aged 12–15 and 16–17 years, VE 14–149 days after dose 2 was 92% and 94%, respectively; VE ≥150 days after dose 2 was 73% and 88%, respectively. All eligible children and adolescents should remain up to date with recommended COVID-19 vaccinations, including a booster dose for those aged 12–17 years.
Emergency Department and Urgent Care Encounters
Among 39,217 eligible encounters at 306 ED and UC facilities, 23.4%, 46.2%, and 30.3% were among persons aged 5–11, 12–15, and 16–17 years. Most encounters among adolescents aged 12–15 years and 16–17 years occurred during the Delta predominant period (14,491 [79.9%] and 8,800 [74.0%], respectively); among children aged 5–11 years, most (6,424 [70.0%]) occurred during the Omicron predominant period, reflecting differences in the dates when vaccines became available for the respective age groups.
Among children aged 5–11 years, VE of 2 doses received 14–67 days earlier against COVID-19–associated ED and UC encounters was 46%. Among adolescents aged 12–15 and 16–17 years, VE of 2 doses 14–149 days earlier against COVID-19–associated ED and UC encounters was 83% and 76%, respectively; VE was significantly lower for 2 doses received ≥150 days earlier (38% and 46%, respectively).
Among adolescents aged 16–17 years, VE after receipt of a third dose ≥7 days earlier increased to 86%, significantly higher than the VE of 2 doses received ≥150 days earlier. The number of observations was insufficient to estimate 3-dose VE for adolescents aged 12–15 years.
Compared with the Delta predominant period, estimated 2-dose VE for adolescents aged 12–15 and 16–17 years declined significantly once Omicron became the predominant variant: among adolescents aged 16–17 years, VE of 2 doses received ≥150 days earlier against COVID-19–associated ED and UC encounters declined from 77% during Delta predominance to a null VE (–3%) during Omicron predominance; however, effectiveness of a third dose received ≥7 days earlier against COVID-19–associated ED and UC encounters during Omicron predominance was 81%. Among children aged 5–11 years, VE of 2 doses received 14–67 days earlier against COVID-19–associated ED and UC encounters during Omicron predominance was 51%.
Receipt of 2 Pfizer-BioNTech vaccine doses in persons aged 12–17 years provided a high level of protection (>90%) against COVID-19–associated hospitalizations within 149 days of receipt of the second dose. VE point estimates for second dose received ≥150 days earlier were 73% to 88%; however, differences by time since vaccination were not statistically significant. Additional data are needed to better understand duration of protection against COVID-19–associated hospitalization in adolescents aged 12–17 years, the protection from 3 doses, and the level of protection among children aged 5–11 years.
These findings are consistent with previously published data showing high effectiveness of the Pfizer-BioNTech vaccine among adolescents before Omicron became the predominant variant, and with data from adults demonstrating relatively higher protection against more severe outcomes. These findings are also consistent with data showing a decline in mRNA VE over time since receipt of the second dose among adolescents and adults. The findings in this report also align with studies among adults that report lower VEs during Omicron variant predominance and an increase in VE after receipt of a third vaccine dose.
