Takeaways:
- A study assessed the effectiveness of the BNT162b2 COVID-19 vaccine in children and adolescents during the Delta and Omicron variant periods.
- The investigation used electronic health record (EHR) data from a national network of US pediatric medical centers and included adolescents aged 12 to 20 years during the Delta phase and children aged 5 to 11 years and adolescents aged 12 to 20 years during the Omicron phase.
- The BNT162b2 vaccine showed approximately 98.4% effectiveness (95% CI, 98.1%-98.7%) for adolescents in the Delta period and 74.3% effectiveness (CI 72.2%-76.2%) against documented infection in children during the Omicron period.
- Vaccine effectiveness remained stable during the Delta period but declined against Omicron after four months, stabilizing afterward with wider confidence intervals.
- The BNT162b2 vaccine demonstrated moderate effectiveness against the Omicron variant in preventing severe diseases, with high effectiveness against the Delta variant, highlighting its pivotal role in reducing SARS-CoV-2 transmission and minimizing COVID-19-related impacts in children and adolescents.
The BNT162b2 COVID-19 vaccine (Pfizer, BioNTech) was effective for various COVID-19-related outcomes in children and adolescents amid the Delta and Omicron variant periods, according to a recently published study in Annals of Internal Medicine.
On May 10, 2021, the FDA expanded emergency use of the BNT162b2 messenger RNA COVID-19 vaccine to adolescents aged 12 to 15 years, and to children aged 5 to 11 years on October 29, 2021.
Forty percent of those aged 5 to 11 years and 72% of those aged 12 to 18 years received at least 1 dose by April 5, 2023, according to the Centers for Disease Control and Prevention (CDC). Randomized clinical trials of the BNT162b2 vaccine took place before emergence of the Omicron variant.
As a result, investigators sough to assess the effectiveness of the BNT162b2 vaccine in preventing infection and severe disease “with various strains of the SARS-CoV-2 virus in previously uninfected children and adolescents.”
Previous studies had limited follow-up periods. The investigators used electronic health record (HER) data from a national network of US pediatric medical centers during the periods when Delta and Omicron variants were predominant, addressing timing gaps in the effectiveness of the BNT162b2 vaccine.
The investigators used 3 study cohorts: adolescents aged 12 to 20 years during the Delta phase and children aged 5 to 11 years and adolescents aged 12 to 20 years during the Omicron phase. No previous COVID-19 vaccination or documented SARS-CoV-2 infection was part of inclusion criteria.
Vaccination was the intervention, compared to no receipt of any COVID-19 vaccine. The investigators focused primarily on the BNT162b2 vaccine since it covered more than 85% of documented vaccinations in the study population.
Outcomes included SARS-CoV-2 infection, mild COVID-19, moderate or severe COVID-19, and intensive care unit (ICU) admission with COVID-19, with classification defined “on the basis of the symptoms and health conditions diagnosed from 7 days before to 13 days after the date of a documented COVID-19 infection,” the investigators wrote.
There were 77,392 adolescents (45,007 vaccinated) included during the Delta phase and 111,539 children (50,398 vaccinated) and 56,080 adolescents (21,180 vaccinated) during the Omicron phase.
Effectiveness of the BNT162b2 vaccine was approximately 98.4% (95% CI, 98.1%-98.7%) for adolescents in the Delta period. Against documented infection and among children in the Omicron period, the vaccine was 74.3% effective (CI 72.2%-76.2%). It was 85.5% effective (CI, 83.3%-87.1%) in adolescents in the Omicron period.
In the Delta period, vaccine effectiveness “remained stable” throughout the study follow-up period. Four months after the first dose, the effectiveness of the vaccine against Omicron declined 82.3% (CI 77.9%-85.8%) to 70.6% (CI 65.9%-74.6%) for children and from 91.3% (CI 87.6%-94.0%) to 82.9% (CI 79.0%-86.1%).
Investigators noted that vaccine effectiveness stabilized after the initial decline, though corresponding Cis were “much wider, indicating higher levels of uncertainty.”
Higher levels of vaccine effectiveness were observed against moderate or severe COVID-19 (75.5% [CI 69.0%-81.0%]) and ICU admission with COVID-19 (84.9% [CI 64.8%-93.5%]).
For adolescents with documented Omicron infection, effectiveness against moderate or severe COVID-19 was 84.8% (CI 77.3%-89.9%) and 91.5% effective against ICU admission with COVID-19 (CI 69.5%-97.6%).
The study did not reveal a statistically significant elevated risk for cardiac complications for vaccinated adolescents in the Delta period. A lower risk was observed in the vaccinated group during the Omicron variant period.
The investigators concluded that the BNT162b2 vaccine for preventing severe diseases and infection of the Omicron variant demonstrated moderate effectiveness, and high effectiveness against the Delta variant.
They wrote, “Our assessment of vaccine effectiveness across diverse outcomes underscores the vaccine's pivotal role in reducing SARS-CoV-2 transmission, minimizing COVID-19–related sick leaves, and alleviating economic burdens during the pandemic.”
Reference:
Wu Q, Tong J, Zhang B, et al. Real-world effectiveness of bnt162b2 against infection and severe diseases in children and adolescents. Ann Intern Med. Published online January 9, 2024:M23-1754. doi:10.7326/M23-1754
