Study reports substantial loss of protection one month after complete SARS-CoV-2 BNT162b2 immunization in children

By Tarun Sai LomteReviewed by Aimee MolineuxMar 2 2022

A recent study posted to the medRxiv* preprint server evaluated the efficacy of Pfizer’s BNT162b2 vaccine in children aged 17 years or younger after the emergence of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) Omicron variant.

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

Coronavirus disease 2019 (COVID-19) infections have been diagnosed in more than 0.8 million individuals aged 17 years or lower in the New York State (NYS), the United States (US). Although observational studies and randomized trials, conducted during the SARS-CoV-2 Delta or preceding waves, observed that the BNT162b2 vaccine is effective against COVID-19 infection in those aged 5 – 17 years. Kids aged 5 – 11 years receive a 10 µg dose of vaccine compared to 30 µg for 12 – 17 years. However, real-world vaccine effectiveness (VE) remains poor for the former cohort, especially since the emergence of the Omicron variant.

The study

In the current study, researchers assess VE in BNT162b2 vaccinees aged ≤ 17 years during the Omicron wave of COVID-19 infections. Three databases linked to analyze the COVID-19 outcomes in children in NYS were utilized – citywide immunization registry (CIR), NYS immunization information system (NYSIIS), and the electronic clinical laboratory reporting system (ECLRS). CIR and NYSISS track vaccination data for New York City (NYC) and NYS, respectively, while ECLRS contains COVID-19 test reports. The Health Electronic Response Data System (HERDS) stores inpatient data and new COVID-19 admissions.

COVID-19 outcomes were compared between fully vaccinated and non-vaccinated children. The authors assessed two outcomes: a) COVID-19 cases reported to ECLRS with a positive nucleic acid or antigen test and b) new COVID-19 admissions based on HERDS inputs. SARS-CoV-2 cases and hospital admissions were counted weekly for vaccinated and non-vaccinated children between November 29, 2021, and January 30, 2022. Incidence rate ratios (IRR), measured as the ratio of non-vaccinated rate to vaccinated rate, were determined, and VE was computed as 1-(1/IRR). In addition, the time since vaccination was examined for children fully vaccinated between December 13, 2021, and January 2, 2022.

Findings

In the NYS, 365,502 (23.4%) of children aged 5 – 11 years and 852,384 (62.4%) of children between 12 and 17 years were fully vaccinated by January 30, 2022. IRR for COVID-19 cases dropped from 6.7% with a VE of 85% at the start of the study to 2.9% (VE = 66%) by December 13, 2021, and 2% (VE  = 51%) by January 24 for 12 – 17-year-old children.

For those aged 5 – 11 years, IRR dropped to 1.1% (VE = 12%) by January 24. Protection against hospitalization was higher than that against COVID-19 infections. IRR for hospitalization was 1.9 with a VE of 48% for 5 – 11 years by January 24, 2022, compared to 3.7 (VE = 73%) for the 12 – 17-year group. During the week of January 24, 2022, VE against COVID-19 infection for an 11-year-old kid was 11% lower than 67% for a 12-year-old.

For the time since vaccination of 12 – 17 years, IRR was 4.3 with a VE of 76% in ≤ 13 days since complete vaccination, which dropped to 2.3 (VE = 56%) by 4 – 5 weeks after full immunization. Likewise, IRR was 2.9 (VE = 65%) for the 5 – 11 age group at 13 days or less since complete vaccination, which reduced to 1.1 (VE = 12%) by 28 to 34 days after complete vaccination.

Conclusion

Overall, the authors observed a rapid decline in VE for the 5 – 11-year age group. A similar reduction was observed for children aged 12 – 17 years, but the decrease was less pronounced than the younger cohort. Moreover, younger children had a substantial loss of protection by one month after complete immunization.

The marked reduction of VE in 11-year-olds relative to 12-year-olds could be attributed to the lower vaccine dose (10 µg) in the 5 – 11 age group. Therefore, an appropriate number of vaccine doses and quantity per dose should be optimized for improved protection.

The authors could not include COVID-19 infections confirmed at residences as they are not reported. Home testing increased during the study period due to the Omicron surge, affecting the observed estimates.

The study findings underpin the protection conferred by vaccination against severe COVID-19 in young children, albeit the observation of rapid loss of protection against infection marked by the appearance of the SARS-CoV-2 Omicron variant.

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources