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COVID-19

COVID-19 Vaccine Effectiveness in Children and Adolescents Exposed

Strategic Insights

— 1 min read

Researchers from the University of Padua in Padua, Italy, have made new findings on the impact of prior SARS-CoV-2 infection on COVID-19 vaccine effectiveness in children and adolescents in Norway and Italy. The study, published in the journal Vaccines, analyzed data from 626,537 children and adolescents in Norway and 38,938 in Italy, and found that a single dose of the vaccine did not reduce the risk of infection among SARS-CoV-2-naive individuals in Norway, but was associated with an 8% risk reduction in Italy. The study also found that hybrid immunity, combining prior SARS-CoV-2 infection and vaccination, provided greater protection against reinfection compared to vaccine-induced immunity alone.

Key Takeaways:

  • A single dose of the vaccine did not reduce the risk of infection among SARS-CoV-2-naive individuals in Norway (HR: 1.05; 95% CI: 1.04-1.07), but was associated with an 8% risk reduction in Italy (HR: 0.92; 95% CI: 0.88-0.96).
  • Among individuals with a recent prior infection (within 12 months), vaccination was associated with a reduced risk of reinfection in Norway (HR: 0.10; 95% CI: 0.05-0.13), but not in Italy (HR: 1.22; 95% CI: 0.83-1.80).
  • Hybrid immunity provided greater protection against (re-)infection compared to vaccine-induced immunity alone, with a 26% risk reduction observed in Norway (HR = 0.74; 95% CI = 0.47-0.1.16) and an 86% reduction in Italy (HR = 0.14; 95% CI = 0.09-0.21).
  • The study included 626,537 children and adolescents in Norway and 38,938 in Italy.
  • The researchers found that continued research and booster strategies are essential to sustain protection and mitigate transmission.

Statistics:

  • A single dose of the vaccine was associated with an 8% risk reduction in Italy.
  • Hybrid immunity provided a 26% risk reduction in Norway.
  • Hybrid immunity provided an 86% reduction in Italy.
  • The study included data from 626,537 children and adolescents in Norway and 38,938 in Italy.
  • The researchers found that vaccination was associated with a reduced risk of reinfection in Norway among individuals with a recent prior infection (within 12 months).

Sources:

  • Impact of Prior SARS-CoV-2 Infection on COVID-19 Vaccine Effectiveness in Children and Adolescents in Norway and Italy. Vaccines, 2025,13(7):698. (Vaccines - http://www.mdpi.com/journal/vaccines)
  • Medical Letter on the CDC & FDA. August 17, 2025; p 296.

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