IMPORTANCEAssessing COVID-19 vaccine performance against the rapidly spreading SARS-CoV-2 Omicron variant is critical to inform public health guidance.OBJECTIVE To estimate the association between receipt of 3 doses of Pfizer-BioNTech BNT162b2 or Moderna mRNA-1273 vaccine and symptomatic SARS-CoV-2 infection, stratified by variant (Omicron and Delta). DESIGN, SETTING, AND PARTICIPANTSA test-negative case-control analysis among adults 18 years or older with COVID-like illness tested December 10, 2021, through January 1, 2022, by a national pharmacy-based testing program (4666 COVID-19 testing sites across 49 US states).EXPOSURES Three doses of mRNA COVID-19 vaccine (third dose Ն14 days before test and Ն6 months after second dose) vs unvaccinated and vs 2 doses 6 months or more before test (ie, eligible for a booster dose). MAIN OUTCOMES AND MEASURESAssociation between symptomatic SARS-CoV-2 infection (stratified by Omicron or Delta variants defined using S-gene target failure) and vaccination (3 doses vs unvaccinated and 3 doses vs 2 doses). Associations were measured with multivariable multinomial regression. Among cases, a secondary outcome was median cycle threshold values (inversely proportional to the amount of target nucleic acid present) for 3 viral genes, stratified by variant and vaccination status.RESULTS Overall, 23 391 cases (13 098 Omicron; 10 293 Delta) and 46 764 controls were included (mean age, 40.3 [SD, 15.6] years; 42 050 [60.1%] women). Prior receipt of 3 mRNA vaccine doses was reported for 18.6% (n = 2441) of Omicron cases, 6.6% (n = 679) of Delta cases, and 39.7% (n = 18 587) of controls; prior receipt of 2 mRNA vaccine doses was reported for 55.3% (n = 7245), 44.4% (n = 4570), and 41.6% (n = 19 456), respectively; and being unvaccinated was reported for 26.0% (n = 3412), 49.0% (n = 5044), and 18.6% (n = 8721), respectively. The adjusted odds ratio for 3 doses vs unvaccinated was 0.33 (95% CI, 0.31-0.35) for Omicron and 0.065 (95% CI, 0.059-0.071) for Delta; for 3 vaccine doses vs 2 doses the adjusted odds ratio was 0.34 (95% CI, 0.32-0.36) for Omicron and 0.16 (95% CI, 0.14-0.17) for Delta. Median cycle threshold values were significantly higher in cases with 3 doses vs 2 doses for both Omicron and Delta (

IMPORTANCEEfficacy of 2 doses of the BNT162b2 COVID-19 vaccine (Pfizer-BioNTech) against COVID-19 was high in pediatric trials conducted before the SARS-CoV-2 Omicron variant emerged. Among adults, estimated vaccine effectiveness (VE) of 2 BNT162b2 doses against symptomatic Omicron infection was reduced compared with prior variants, waned rapidly, and increased with a booster. OBJECTIVE To evaluate the association of symptomatic infection with prior vaccination with BNT162b2 to estimate VE among children and adolescents during Omicron variant predominance. DESIGN, SETTING, AND PARTICIPANTS A test-negative, case-control analysis was conducted using data from 6897 pharmacy-based, drive-through SARS-CoV-2 testing sites across the US from a single pharmacy chain in the Increasing Community Access to Testing platform. This analysis included 74 208 tests from children 5 to 11 years of age and 47 744 tests from adolescents 12 to 15 years of age with COVID-19-like illness who underwent SARS-CoV-2 nucleic acid amplification testing from December 26, 2021, to February 21, 2022.EXPOSURES Two BNT162b2 doses 2 weeks or more before SARS-CoV-2 testing vs no vaccination for children; 2 or 3 doses 2 weeks or more before testing vs no vaccination for adolescents (who are recommended to receive a booster dose).MAIN OUTCOMES AND MEASURES Symptomatic infection. The adjusted odds ratio (OR) for the association of prior vaccination and symptomatic SARS-CoV-2 infection was used to estimate VE: VE = (1 − OR) × 100%.RESULTS A total of 30 999 test-positive cases and 43 209 test-negative controls were included from children 5 to 11 years of age, as well as 22 273 test-positive cases and 25 471 test-negative controls from adolescents 12 to 15 years of age. The median age among those with included tests was 10 years (IQR, 7-13); 61 189 (50.2%) were female, 75 758 (70.1%) were White, and 29 034 (25.7%) were Hispanic/Latino. At 2 to 4 weeks after dose 2, among children, the adjusted OR was 0.40 (95% CI, 0.35-0.45; estimated VE, 60.1% [95% CI, 54.7%-64.8%]) and among adolescents, the OR was 0.40 (95% CI, 0.29-0.56; estimated VE, 59.5% [95% CI, 44.3%-70.6%]). During month 2 after dose 2, among children, the OR was 0.71 (95% CI, 0.67-0.76; estimated VE, 28.9% [95% CI, 24.5%-33.1%]) and among adolescents, the OR was 0.83 (95% CI, 0.76-0.92; estimated VE, 16.6% [95% CI, 8.1%-24.3%]). Among adolescents, the booster dose OR 2 to 6.5 weeks after the dose was 0.29 (95% CI, 0.24-0.35; estimated VE, 71.1% [95% CI, 65.5%-75.7%]).CONCLUSIONS AND RELEVANCE Among children and adolescents, estimated VE for 2 doses of BNT162b2 against symptomatic infection was modest and decreased rapidly. Among adolescents, the estimated effectiveness increased after a booster dose.

On November 22, 2022, this report was posted as an MMWR Early Release on the MMWR website (https://www.cdc.gov/mmwr).On September 1, 2022, bivalent COVID-19 mRNA vaccines, composed of components from the SARS-CoV-2 ancestral and Omicron BA.4/BA.5 strains, were recommended by the Advisory Committee on Immunization Practices (ACIP) to address reduced effectiveness of COVID-19 monovalent vaccines during SARS-CoV-2 Omicron variant predominance (1). Initial recommendations included persons aged ≥12 years (Pfizer-BioNTech) and ≥18 years (Moderna) who had completed at least a primary series of any Food and Drug Administrationauthorized or -approved monovalent vaccine ≥2 months earlier (1). On October 12, 2022, the recommendation was expanded to include children aged 5-11 years. At the time of recommendation, immunogenicity data were available from clinical trials of bivalent vaccines composed of ancestral and Omicron BA.1 strains; however, no clinical efficacy data were available. In this study, effectiveness of the bivalent (Omicron BA.4/BA.5-containing) booster formulation against symptomatic SARS-CoV-2 infection was examined using data from the Increasing Community Access to Testing (ICATT) national SARS-CoV-2 testing program.* During September 14-November 11, 2022, a total of 360,626 nucleic acid amplification tests (NAATs) performed at 9,995 retail pharmacies for adults aged ≥18 years, who reported symptoms consistent with COVID-19 at the time of testing and no immunocompromising conditions, were included in the analysis. Relative vaccine effectiveness (rVE) of a bivalent booster dose compared with that of ≥2 monovalent vaccine doses among persons for whom 2-3 months and ≥8 months had elapsed since last monovalent dose was 30% and 56% among persons aged 18-49 years, 31% and 48% among persons aged 50-64 years, and 28% and 43% among persons aged ≥65 years, respectively. Bivalent mRNA booster doses provide additional protection against symptomatic SARS-CoV-2 in immunocompetent persons who previously received monovalent vaccine only, with relative benefits increasing with time since receipt of the most recent monovalent vaccine dose. Staying up to date with COVID-19 vaccination, including getting a bivalent booster dose when eligible, is critical to maximizing protection against COVID-19 (1). * https://www.cdc.gov/icatt/index.html