What is already known about this topic? 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.

What is added by this report? 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%.

What are the implications for public health practice? 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 (1–3). 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 (4–6); however, data on VE against the SARS-CoV-2 B.1.1.529 (Omicron) Variants 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.

VISION Network VE Methods have been previously published (7). In brief, eligible medical encounters were defined as ED and UC encounters and hospitalizations among persons aged ≥5 years with a COVID-19–like illness Diagnosis¶ who had received SARS-CoV-2 molecular tTesting (primarily by reverse transcription–polymerase chain reaction assay) during the 14 days before through 72 hours after the encounter. For adolescents aged 16–17 years, the study period began when COVID-19 vaccines were recommended and became available to persons aged ≥16 years at each study site (April–May 2021).** For children aged 5–11 years and adolescents aged 12–15 years, the study period began 5 weeks after the Pfizer-BioNTech vaccine was recommended for their age group.†† The dates when the Delta and Omicron Variantss became predominant (accounted for >50% of sequenced Viruses) were determined for each study site based on state and national Surveillance data.§§ Patients were excluded if they 1) were vaccinated before the CDC recommendation date for their age group, 2) received a third dose before booster doses were recommended for their age group, 3) received a booster dose <5 months after dose 2, 4) received 1 or >3 doses of the vaccine, or 5) if <14 days had elapsed since receipt of dose 2 or <7 days since dose 3. Patients who were likely immunocompromised based on Diagnosis codes were also excluded.¶¶ VE was estimated using a case-control test-negative design comparing the odds of a positive SARS-CoV-2 test result between vaccinated (received 2 doses ≥14 days earlier or 3 doses ≥7 days earlier) and unvaccinated (received no doses) patients using multivariable logistic regression models*** (7). VE was not calculated for exposure categories with fewer than 20 encounters or with no SARS-CoV-2 test–positive cases. A statistically significant difference in VE or distributions of vaccination or infection status was indicated by nonoverlapping 95% CIs or standardized mean or proportion differences ≥0.2. All statistical analyses were conducted using R software (version 4.1.2; R Foundation). This study was reviewed and approved by the institutional review boards at participating sites or under a reliance agreement with the Westat, Inc. institutional review board.

Suggested citation for this article: Klein NP, Stockwell MS, Demarco M, et al. Effectiveness of COVID-19 Pfizer-BioNTech BNT162b2 mRNA Vaccination in Preventing COVID-19–Associated Emergency Department and Urgent Care Encounters and Hospitalizations Among Nonimmunocompromised Children and Adolescents Aged 5–17 Years — VISION Network, 10 States, April 2021–January 2022. MMWR Morb Mortal Wkly Rep. ePub: 1 March 2022.

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