In a recent article posted on the medRxiv* preprint server, researchers have demonstrated the short-term protection conferred by the vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) BNT162b2 in adolescents and children.
The Coronavirus Disease 2019 (COVID-19) Pfizer-BioNTech (BNT162b2) vaccine has lower efficacy against the SARS-CoV-2 Omicron variant than the Delta and other variants. In addition, the actual efficacy of the BNT162b2 vaccine against Omicron infection in children and adolescents is limited.
Shortly before the SARS-CoV-2 Omicron outbreak, the two-dose BNT162b2 vaccination for children and the third BNT162b2 injection for adolescents were approved in Israel. The BNT162b2 vaccination was approved in Israel on June 2, 2021 for adolescents ages 12 to 15, and a booster dose was approved on August 29, 2021 for those who had received the second vaccine at least five months earlier. From November 23, 2021, children aged 5-11 years received a two-dose BNT162b2 vaccination with one-third the amount used for children aged 12 and older. However, the impact of these vaccinations on Omicron-confirmed SARS-CoV-2 infection rates in these populations is still unknown.
About the study
In the current work, the researchers analyzed data from Israel to examine the efficacy of the two-dose BNT162b2 regimen for children aged five to 11 years and the booster injection for adolescents aged 12 to 15 years. The authors collected information for the Omicron BA. 1 sublineage-dominated time frame: Between December 26, 2021 and January 8, 2022 in Israel. They noted that credible efficacy estimates for the time after January 8, 2022 were difficult to obtain due to substantial policy changes in COVID-19 testing, contact isolation and school quarantine.
The scientists analyzed data from Israel’s Ministry of Health database, which contained information on all vaccinations and tests performed in Israel. The study cohort included children (5 to 10 years) and adolescents (12 to 15 years) who had received a COVID-19 vaccine or had undergone at least one state-regulated antigen or polymerase chain reaction (PCR) test before December 1, 2021. The team omitted the 11-year-old age group because current data only includes age in years and vaccination dates for 11- and 12-year-olds varied.
The researchers evaluated the rates of confirmed SARS-CoV-2 infection in children aged five to 10 years 14 to 35 days after receiving the second dose with an internal control cohort of children three to seven days after receiving the first injection when vaccination had not yet been completed. ineffective. Similarly, they compared confirmed COVID-19 rates in adolescents 12 to 15 years old 14 to 60 days after receiving a booster injection with a control cohort of adolescents three to seven days after receiving the booster dose. The authors used Poisson regression to control for gender, age, calendar week, exposure, and socioeconomic level.
Results and conclusions
Overall, the study results showed that the COVID-19 BNT162b2 vaccination provided an initial nearly two-fold improvement in immunity against SARS-CoV-2 infection in children aged five to 10 years. The estimated incidence of confirmed COVID-19 in the five to ten age bracket was 2.3 times lower in the second dose cohort compared to the internal control population.
In addition, the present analysis found that a recent booster dose of BNT162b2 in adolescents reduced SARS-CoV-2 infections three to four fold compared to the internal control. Specifically, the third dose reduced confirmed COVID-19 rates by 3.3 fold in adolescents.
The authors found that different testing habits did not explain the reduced confirmed SARS-CoV-2 infection rates in the vaccinated groups relative to the unvaccinated groups. In all age groups, the unvaccinated cohorts tested less frequently than the vaccinated groups, implying that the predicted protection may be underestimated compared to unvaccinated individuals.
While the vaccine-naïve cohorts had lower test rates than the vaccinated groups, the subjects in the internal control had a slightly higher test rate than the second-dose vaccination group in the five to 10-year age range, which could contribute to an overestimation of protection. of the vaccine. The subjects in the internal control had a lower test rate than the booster group in the vaccinated age group of 12 to 15 years, probably indicating that the booster injection offers a better degree of protection than expected in this study.
In summary, the current study illustrated an assessment of the temporary protection of the COVID-19 BNT162b2 vaccine against confirmed SARS-CoV-2 infection in adolescents and children. Compared to the corresponding internal control cohorts, the recent vaccination with two doses of the BNT162b2 vaccine in children and the last booster injection in adolescents reduced the risk of confirmed SARS-CoV-2 infection. The authors noted that future research was needed to determine how long this protection lasts and how well it protects against other COVID-19 outcomes, including pulmonary COVID and pediatric inflammatory multisystem syndrome transiently associated with SARS-CoV-2 (PIMS- TS).
medRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, should guide clinical practice/health-related behavior, or be treated as established information.