Author(s):
Soares, Patricia ; Machado, Ausenda ; Nicolay, Nathalie ; Monge, Susana ; Sacco, Chiara ; Hansen, Christian Holm ; Meijerink, Hinta ; Martínez-Baz, Iván ; Schmitz, Susanne ; Humphreys, James ; Fabiani, Massimo ; Echeverria, Aitziber ; AlKerwi, Ala'a ; Nardone, Anthony ; Mateo-Urdiales, Alberto ; Castilla, Jesús ; Kissling, Esther ; Nunes, Baltazar ; VEBIS-Lot 4 working group
Date: 2025
Persistent ID: http://hdl.handle.net/10400.18/10519
Origin: Repositório Científico do Instituto Nacional de Saúde
Subject(s): COVID-19 Vaccines; Electronic Health Records; Paediatrics; Vaccine Effectiveness; Europe; Cuidados de Saúde; Infecções Respiratórias.; VEBIS-LOT 4
Description
Background: During the first year of the COVID-19 pandemic, vaccination programmes targeted children and adolescents to prevent severe outcomes of SARS-CoV-2 infection. Aim: To estimate COVID-19 vaccine effectiveness (VE) against hospitalisation due to COVID-19 in the paediatric population, among those with and without previously documented SARS-CoV-2 infection. Methods: We established a fixed cohort followed for 12 months in Denmark, Norway, Italy, Luxembourg, Navarre (Spain) and Portugal using routine electronic health registries. The study commenced with paediatric COVID-19 vaccination campaign at each site between June 2021 and January 2022. The outcome was hospitalisation with a laboratory-confirmed SARS-CoV-2 infection or COVID-19 as the main diagnosis. Using Cox proportional hazard models, VE was estimated as 1 minus the confounder-adjusted hazard ratio of COVID-19 hospitalisation between vaccinated and unvaccinated. A random-effects meta-analysis was used to pool VE estimates. Results: We included 4,144,667 5-11-year-olds and 3,861,841 12-17-year-olds. In 12-17-year-olds without previous infection, overall VE was 69% (95% CI: 40 to 84). VE declined with time since vaccination from 77% ≤ 3 months to 48% 180-365 days after immunisation. VE was 94% (95% CI: 90 to 96), 56% (95% CI: 3 to 80) and 41% (95% CI: -14 to 69) in the Delta, Omicron BA.1/BA.2 and BA.4/BA.5 periods, respectively. In 12-17-year-olds with previous infection, one dose VE was 80% (95% CI: 18 to 95). VE estimates were similar for 5-11-year-olds but with lower precision. Conclusion: Vaccines recommended for 5-17-year-olds provided protection against COVID-19 hospitalisation, regardless of a previously documented infection of SARS-CoV-2, with high levels of protection in the first 3 months of the vaccination.
Key public health message: - What did you want to address in this study and why? Vaccination programmes were launched in the first year of the pandemic including for children and adolescents to prevent severe outcomes of SARS-CoV-2 infection, despite being rare in younger age groups. We assessed vaccine effectiveness (VE) of COVID-19 vaccines across six European countries in 5–17-years-olds with and without previous SARS-CoV-2 infection. Our 12-month study period allowed examination of VE against Delta and Omicron variants. ; - What have we learnt from this study? Overall, vaccines recommended for 5–17-year-olds prevented two thirds of COVID-19 hospitalisations, regardless of a previously documented infection of SARS-CoV-2. The level of protection was the highest 3 months following vaccination. Although VE declined over time, vaccinees remained at lower risk of hospitalisation during the 12-month study period vs those unvaccinated. Vaccine effectiveness tended to be lower during Omicron variant circulation.; - What are the implications of your findings for public health? Monitoring COVID-19 VE in population subgroups, such as children and adolescents, is important to inform future vaccination strategies. Our results showed that vaccination protected children against severe COVID-19 during Delta- and Omicron-circulating periods. We also highlighted valuable use of electronic health registeries to conduct VE studies in specific subgroups where severe outcomes were rare, vs more complex approaches using primary data.
