The incidence of Covid-19 infection was 8 times higher in unvaccinated school-going students compared to those who were vaccinated, according to a study from the Duke University School of Medicine in North Carolina in the USA.

Researchers recruited 1128 students, aged 11-19 years in this prospective study conducted from August 1, 2021 (Day 0) to November 12, 2021 (Day 103) to study the impact of Covid-19 vaccination. These students attended Grades 6 to 12 at a private school. The school had mandated wearing masks indoors and hybrid classes (online and offline). This study was conducted during a surge in community cases caused predominantly by the delta SARS-CoV-2 variant. The incidence of infection was measured on Day 103 of the study. “Ventilation systems were upgraded with minimum efficiency reporting value (MERV) 11 filters; high efficiency particulate air (HEPA) filters were not used. Physical distancing was minimal, and there was no routine surveillance testing for students or staff.”

Out of the 1128 students included in the study, 829 (73.5%) were vaccinated, while the remaining 299 (26.5%) were unvaccinated. There were 27 infections altogether. Twenty (6.7%) unvaccinated students got infected during the study; 16 of them developed symptoms. Among the vaccinated group, only seven (0.8%) developed the infection and five (71%) were symptomatic. Only two students were classified as within-school transmissions, both cases did not wear masks and acquired infection from exposure to unvaccinated index cases.

Among the unvaccinated students, the incidence of confirmed infection was 8.2 times higher, and the incidence of symptomatic infection compared with vaccinated students was 9.2 times higher compared to the vaccinated students. The unadjusted vaccine effectiveness against confirmed infection was 87.8%, while the vaccine effectiveness against symptomatic infection was 89.1%.

This study has demonstrated that vaccination significantly reduced the incidence of Covid-19 among school-going adolescents during the delta surge. Aside from vaccination, other protective measures like masking also kept the infection at bay in this group. These findings assume importance now that schools have reopened as they highlight the significant role of vaccination in preventing or reducing within-school transmission and continuing in-person classes. Everyone eligible must be encouraged to take the vaccine.

Reference

1. Thakkar PV, et al. COVID-19 incidence among 6th-12th grade students by vaccination status. Pediatrics. 2022 Feb 22. doi: 10.1542/peds.2022-056230.