Estimated BNT162b2 Vaccine Effectiveness Against Infection With Delta and Omicron Variants Among US Children 5 to 11 Years of Age

Abstract

ImportanceData describing the vaccine effectiveness (VE) and durability of BNT162b2 among children 5 to 11 years of age are needed.ObjectiveTo estimate BNT162b2 VE against SARS-CoV-2 infection among children aged 5 to 11 years during Delta and Omicron variant–predominant periods and to further assess VE according to prior SARS-CoV-2 infection status and by sublineage during the Omicron variant–predominant period.Design, Setting, and ParticipantsThis test-negative case-control study was conducted from November 2 to December 9, 2021 (Delta variant), and from January 16 to September 30, 2022 (Omicron variant), among 160 002 children tested at a large national US retail pharmacy chain, for SARS-CoV-2 via polymerase chain reaction (PCR); 62 719 children were tested during the Delta period, and 97 283 were tested during the Omicron period.ExposureVaccination with BNT162b2 before SARS-CoV-2 testing vs no vaccination.Main Outcomes and MeasuresThe primary outcome was SARS-CoV-2 infection confirmed by PCR (regardless of the presence of symptoms), and the secondary outcome was confirmed symptomatic infection. Adjusted estimated VE was calculated from multilevel logistic regression models.ResultsA total of 39 117 children tested positive and 131 686 tested negative for SARS-CoV-2 (total, 170 803; 84 487 [49%] were boys; mean [SD] age was 9 [2] years; 74 236 [43%] were White non-Hispanic or non-Latino; and 37 318 [22%] were Hispanic or Latino). Final VE analyses included 160 002 children without SARS-CoV-2 infection less than 90 days prior. The VE of 2 doses of BNT162b2 against Delta was 85% (95% CI, 80%-89%; median follow-up, 1 month) compared with the Omicron period (20% [95% CI, 17%-23%]; median follow-up, 4 months). The adjusted VE of 2 doses against Omicron at less than 3 months was 39% (95% CI, 36%-42%), and at 3 months or more, it was −1% (95% CI, −6% to 3%). Protection against Omicron was higher among children with vs without infection 90 days or more prior but decreased in all children approximately 3 months after the second dose (58% [95% CI, 49%-66%] with infection vs 37% [95% CI, 34%-41%] without infection at <3 months; 27% [95% CI, 17%-35%] with infection vs −7% [95% CI, −12% to −1%] at ≥3 months without infection). The VE of 2 doses of BNT162b2 at less than 3 months by Omicron sublineage was 40% (95% CI, 36%-43%) for BA.1, 32% (95% CI, 21%-41%) for BA.2/BA.2.12.1, and 50% (95% CI, 37%-60%) for BA.4/BA.5. After 3 months or more, VE was nonsignificant for BA.2/BA.2.12.1 and BA.4/BA.5. The VE of a booster dose was 55% (95% CI, 50%-60%) against Omicron, with no evidence of waning at 3 months or more.Conclusions and RelevanceThis study suggests that, among children aged 5 to 11 years, 2 doses of BNT162b2 provided modest short-term protection against Omicron infection that was higher for those with prior infection; however, VE waned after approximately 3 months in all children. A booster dose restored protection against Omicron and was maintained for at least 3 months. These findings highlight the continued importance of booster vaccination regardless of history of prior COVID-19.

Safety and effectiveness of vaccines against COVID-19 in children aged 5–11 years: a systematic review and meta-analysis

“… 26 , 27 Studies were primarily done in high-income countries (eg, the USA, Canada, and Israel), and assessed a complete primary schedule of BNT162b2 vaccine (n=46 [90%]). Three (6%) studies only assessed the effect of a single dose of either BNT162b2 or mRNA-1273, 28 , 29 , 30 and nine (18%) studies assessed the effect of a monovalent 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 or bivalent (BNT162b2 bivalent [against original strain or omicron BA.4 or BA.5]) 39 booster vaccination ( appendix 1 pp 26–33 ). Participants' age was in line with the authorised age group (ie, 5–11 years for studies on BNT162b2 or BNT162b2 bivalent and 6–11 years for studies on mRNA-1273; appendix 1 pp 26–33 ).…”

“… 40 , 43 , 44 , 47 All reported a substantial reduction in vaccine effectiveness against SARS-CoV-2 infections of at least 15% from the timepoint of first measurement after two-dose vaccination to the timepoint of last measurement ( appendix 1 p 40 ). One study 32 reported vaccine effectiveness against omicron infections after the third dose (vaccine effectiveness 55% [50–60]) and reported no effect of waning protection up to 4 months after the booster.…”

“…One study 32 reported vaccine effectiveness against omicron infections after the third dose (vaccine effectiveness 55% [50–60]) and reported no effect of waning protection up to 4 months after the booster.…”

“… NRSI 3 27 595 per 100 000 12 418 per 100 000 (11 038 to 13 798) VE 55% (50–60); VE ratio 0·45 (0·40–0·50) Up to ≥3 months after third dose 60 574 32 Moderate; downgraded by one level for serious imprecision (one study only) Booster vaccination probably reduces the risk of SARS-CoV-2 infections with omicron. Symptomatic COVID-19 NRSI 2 31 326 per 100 000 19 203 per 100 000 (15 005 to 24 528) VE 36·2% (21·5–48·2); VE ratio 0·638 (0·518–0·749) ≥7 days after second dose to median of 4 months after second dose 3 262 727 32 , 45 , 48 , 49 , 50 , 51 Low; downgraded by two levels for serious inconsistency ( I 2 =92·2%) Primary vaccination series probably slightly reduces the risk of symptomatic COVID-19. NRSI 3 NR § NE VE 61% (55–67); VE ratio 0·39 (0·33–0·45) Up to ≥3 months after third dose 60 574 32 Moderate; downgraded by one level for serious imprecision (one study only) Booster vaccination probably reduces the risk of symptomatic COVID-19.…”

Knowledge on Parental Hesitancy toward COVID-19 Vaccination of Children 5–11 Years Old

“…On the contrary, a further increase in parental hesitancy levels with further reduction of COVID-19 immunization rates in children aged 5–11 years may be evidenced by of the impact of the Omicron SARS-CoV-2 variants and the position taken by some countries regarding the administration of COVID-19 vaccines in children aged 5–11 years. Studies carried out after the emergence of the Omicron variant in December 2021 and published some months later showed that the effectiveness of the BNT162b2 vaccine in 5–11 year-old children was significantly reduced compared to the effectiveness shown in the studies performed for emergency authorization and carried out when the wild virus or earlier variants, including the Delta variant, were circulating [ 45 , 46 , 47 , 48 , 49 ]. A retrospective study carried out in Italy between 17 January and 13 April 2022 which enrolled 2,965,918 immunized children and 1,441,166 controls showed that the effectiveness of the recommended two doses of the BNT162b2 vaccine against infection was only 29.4% and 27.4%, respectively, in fully vaccinated and partially vaccinated children [ 50 ].…”