Reviewed by Erica Stohs, MD, MPH, University of Nebraska
Investigators in Italy sought to answer this important question and their results are published in The Lancet. Between January and mid-April 2022, 35% of Italy’s 2.9 million 5–11-year-olds were fully vaccinated with BNT162b2, and another 4.5% had received one dose only. Through a national immunization registry and the national COVID-19 Integrated Surveillance System which are linked by tax code, investigators determined that ~766,000 cases of SARS-CoV-2 infection and 644 cases of severe COVID-19 (hospitalizations, ICU admissions, and 2 deaths) occurred. Omicron accounted for 80% of SARS-CoV-2 in Italy during the study period.
Vaccine effectiveness in the fully vaccinated group was 29% against any infection and 41% against severe infection. Vaccine effectiveness in the partially vaccinated group was 27% and 38% against any infection and severe infection, respectively. Effectiveness peaked (39% within 14 days of series completion) immediately following vaccination completion and waned by 6-12 weeks following vaccination (21%). Results were roughly comparable to pediatric studies in the US. The Italian study showed lower effectiveness against severe COVID-19 than the US but median days post-vaccination was much longer (71 days vs 34). Authors also suspect many unaccounted asymptomatic infections. The conclusions were that the pediatric vaccines provide modest protection in children, principally against severe disease, during this Omicron wave.
Sacco C, et al. “Effectiveness of BNT162b2 vaccine against SARS-CoV-2 infection and severe COVID-19 in children aged 5-11 years in Italy: a retrospective analysis of January-April, 2022.” The Lancet 2022;400(10346): 97-103. https://doi.org/10.1016/S0140-6736(22)01185-0