In a recent article on the medRxiv* Preprint servers showed researchers the short-term protection offered by vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) BNT162b2 in adolescents and children.
The Pfizer-BioNTech (BNT162b2) coronavirus disease 2019 (COVID-19) vaccine has lower efficacy against the SARS-CoV-2 Omicron variant than Delta and other variants. In addition, the actual efficacy of the BNT162b2 vaccine against Omicron infection in children and adolescents is limited.
Just before the SARS-CoV-2 Omicron outbreak, the BNT162b2 two-dose vaccine for children and the third BNT162b2 vaccine for adolescents were approved in Israel. The BNT162b2 vaccine was approved in Israel on June 2, 2021 for adolescents aged 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. Beginning November 23, 2021, children ages five to 11 received a two-dose BNT162b2 vaccine, using one-third the amount provided to 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, researchers analyzed data from Israel to examine the efficacy of the two-dose BNT162b2 regimen for children ages five to 11 and the booster dose for adolescents ages twelve to 15. The authors collected information for Omicron BA. 1 time frame dominated by sub-lines: between December 26, 2021 and January 8, 2022 in Israel. They noted that significant policy changes on COVID-19 testing, contact isolation and school quarantines have made credible estimates of effectiveness difficult to obtain after January 8, 2022.
The scientists analyzed data from the Israel Ministry of Health’s database, which contained information on all vaccinations and tests carried out in Israel. The study cohort included children (5 to 10 years) and adolescents (12 to 15 years) if they were younger than 1. The team omitted the 11-year-old age group because the current data included only age in years and the Vaccination eligibility dates were different for 11- and 12-year-olds.
The researchers assessed 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 vaccination, as the vaccination not yet completed was ineffective. Likewise, they compared confirmed COVID-19 rates in adolescents aged 12 to 15 years 14 to 60 days after receiving a booster dose with a control group of adolescents three to seven days after receiving the booster dose. The authors used Poisson regression control for gender, age, calendar week, exposure, and socioeconomic level.
Results and Conclusions
Overall, study results showed that COVID-19 BNT162b2 vaccination offered 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 five to ten age categories was 2.3-fold lower in the second dose cohort compared to the internal control population.
In addition, the current analysis revealed that a recent booster vaccination with BNT162b2 in adolescents reduced SARS-CoV-2 infections by three to four times compared to the internal control. Specifically, the third dose reduced confirmed rates of COVID-19 in adolescents by 3.3-fold.
The authors found that different testing habits did not explain the lower confirmed SARS-CoV-2 infection rates in the vaccinated groups compared to the unvaccinated groups. Across all age categories, the unvaccinated cohorts were tested less frequently than the vaccinated groups, implying that the predicted protection may be underestimated compared to unvaccinated individuals.
While the vaccination-naïve cohorts had lower testing rates than the vaccinated groups, the internal controls had a slightly higher testing rate than the second vaccination group in the five to 10 year age range, which may contribute to an overestimation of vaccine protection. Internal control subjects had a lower testing rate than the booster in the vaccinated age group of 12 to 15 years, likely indicating that the booster confers a better level of protection than expected in this study.
In summary, the current investigation illustrates an assessment of the temporary protection of the COVID-19 BNT162b2 vaccine against confirmed SARS-CoV-2 infection in adolescents and children. Recent vaccination with two doses of BNT162b2 vaccine in children and the last booster vaccination in adolescents reduced the risk of confirmed SARS-CoV-2 infection compared to the corresponding internal control cohorts. The authors mentioned that future research is needed to determine how long this protection lasts and how well it protects against other COVID-19 outcomes, including long-term COVID and pediatric multisystem inflammatory syndrome co-occurring with SARS-CoV-2 (PIMS-TS) is associated.
medRxiv publishes preliminary scientific reports that have not been peer-reviewed and therefore should not be relied upon as conclusive, guide clinical practice/health behavior or be treated as established information.