Children immunized with BNT162b2 vaccination show adequate immunity to omicron variant: NEJM

Singapore: Children aged 5 to 11 who received the BNT162b2 vaccine had lower rates of SARS- CoV-2 infection and hospitalization because of Covid-19 states a study published in The New England Journal of Medicine.

The B.1.1.529 (omicron) variant of SARS-CoV-2 has rapidly spread since it was initially discovered in November 2021, dethroning the B.1.617.2 (delta) variant as the predominant strain in several nations. There is a dearth of information on the actual efficacy of vaccinations against the omicron variant in children.

In a recent trial, researchers assessed the BNT162b2 vaccine's efficacy in protecting children aged five to eleven against the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant, Omicron.

Their research revealed that the BNT162b2 vaccination's vaccine efficacy (VE) against all SARS-CoV-2 infections in children aged five to eleven was only 36.8% towards Omicron. However, following vaccination, VE among these children reached 82.7% against short-term hospitalization.

In the proposed investigation, between January 21, 2022, and April 8, 2022, during which Omicron was responsible for over 99% of sequencing SARS-CoV-2 cases in Singapore, data on 255,936 children between the ages of 5 and 11 years was examined by the researchers. With a median gap of 24 days between doses, 67.7% of five to 11-year-olds were fully immunized, while 12% only received one BNT1262b dosage and 20.3% were still unvaccinated.

To calculate the vaccine efficacy (VE) of the BNT162b2 vaccine, researchers evaluated the incidence rate ratio of all known SARS-CoV-2 infections and COVID-19-related hospitalizations among children who had received either partial or full vaccinations. No matter the type of testing method—RT-PCR testing or rapid antigen testing—the study outcomes included the day of hospitalization and the reporting of a positive test result to a parent or guardian (RAT). The study also calculated the VE from the incidence rate ratio of each of the three research findings using the Poisson regression method. This was done for both the one- and two-dose BNT162b2 vaccinations.

Key findings of the study:

 Cumulative incidence rates of all SARS-CoV-2 infections identified PCR-confirmed SARS-CoV-2 infections and hospitalizations linked to Covid-19 were 3303.5, 473.8, and 30.0 per 1 million person-days, respectively, among children who had not received vaccinations.

 According to incidence rate ratios, completely immunized children had substantially higher VEs: 36.8% against all reported infections, 65.3% against SARS-CoV-2 infections validated by RT-PCR, and 82.7% against hospitalization. Relatively, VE against the three study parameters was 13.6%, 24.3%, and 42.3% higher in children who had only received a partial vaccination compared to those who had not received any vaccinations at all.

The authors concluded that with two doses of BNT162b2 compared to one, the protection against hospitalization was stronger (82.7% vs. 42.3%). Altogether, BNT162b2 offered children aged five to eleven years of age a moderate level of defense against illness and infection.

"The findings of this study may provide insights to help decision-makers to assess the advantages against the possible hazards of immunizing youngsters", added the authors.

REFERENCE

Sharon H.X. Tan, M.P.H., Alex R. Cook, Ph.D., Derrick Heng, M.Phil., Benjamin Ong, M.B., B.S., David C. Lye, M.B., B.S., and Kelvin B. Tan, Ph.D. Effectiveness of BNT162b2 Vaccine against Omicron in Children 5 to 11 Years of Age. N Engl J Med 2022; 387:525-532 DOI: 10.1056/NEJMoa2203209