Vaccination effectiveness under risk-adapted outbreak response in two Roma communities, Portugal
Abstract
During a 2025 hepatitis A outbreak in Portimão, southern Portugal, two Roma communities required different public health responses: whole-community vaccination in Cabeço do Mocho, where hygiene and sanitation conditions were deficient, and mainly reactive household-based vaccination in Vale da Arrancada, where residents had potable water and sanitation. We assessed vaccination effectiveness and the consequences of non-vaccination. We conducted a retrospective comparative observational study nested within an outbreak investigation. Residents were classified as vaccinated only if at least 14 days had elapsed between vaccination and symptom onset; otherwise they were classified as unvaccinated. Infection by vaccination status was compared within each community and overall using Fisher’s exact test. By 23 July 2025, 44 outbreak-related cases had been identified. In Cabeço do Mocho, vaccination coverage was 75/107 (70.1%); infection occurred in 2/75 vaccinated versus 11/32 unvaccinated residents (2.7% vs 34.4%; RR = 0.0776; estimated effectiveness 92.2%; p = 0.000021). In Vale da Arrancada, coverage was 21/70 (30.0%); no vaccinated resident became a case, compared with 8/49 unvaccinated residents (0% vs 16.3%; p = 0.094870). Overall, infection occurred in 2/96 vaccinated and 19/81 unvaccinated residents (2.1% vs 23.5%; RR = 0.0888; estimated effectiveness 91.1%; p = 0.000009). Vaccination was associated with markedly lower hepatitis A infection. Whole-community outreach achieved substantially higher coverage than reactive household-based vaccination, while non-vaccination concentrated cases in both communities. These findings support early context-adapted vaccination strategies in socially vulnerable settings during hepatitis A outbreaks.
Key messages: • Whole-community vaccination in the higher-risk setting achieved greater coverage and was associated with lower hepatitis A infection.
• Considering protection only from 14 days after vaccination, cases were concentrated among non-vaccinated residents in both communities.
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BibTeX
@article{medeiros2026vaccination,
title = {{Vaccination effectiveness under risk-adapted outbreak response in two Roma communities, Portugal}},
author = {I F Medeiros and E A Matias and I C Gonçalves and L T Castêdo and J D Ferreira and P A Correia and L C Cadinha and L P Porojan},
journal = {The European Journal of Public Health},
year = {2026},
month = oct,
doi = {10.1093/eurpub/ckag169.1609},
url = {https://doi.org/10.1093/eurpub/ckag169.1609},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Vaccination effectiveness under risk-adapted outbreak response in two Roma communities, Portugal
AU - I F Medeiros
AU - E A Matias
AU - I C Gonçalves
AU - L T Castêdo
AU - J D Ferreira
AU - P A Correia
AU - L C Cadinha
AU - L P Porojan
PY - 2026
DA - 2026/10/01
JO - The European Journal of Public Health
DO - 10.1093/eurpub/ckag169.1609
UR - https://doi.org/10.1093/eurpub/ckag169.1609
AB - During a 2025 hepatitis A outbreak in Portimão, southern Portugal, two Roma communities required different public health responses: whole-community vaccination in Cabeço do Mocho, where hygiene and sanitation conditions were deficient, and mainly reactive household-based vaccination in Vale da Arrancada, where residents had potable water and sanitation. We assessed vaccination effectiveness and the consequences of non-vaccination. We conducted a retrospective comparative observational study nested within an outbreak investigation. Residents were classified as vaccinated only if at least 14 days had elapsed between vaccination and symptom onset; otherwise they were classified as unvaccinated. Infection by vaccination status was compared within each community and overall using Fisher’s exact test. By 23 July 2025, 44 outbreak-related cases had been identified. In Cabeço do Mocho, vaccination coverage was 75/107 (70.1%); infection occurred in 2/75 vaccinated versus 11/32 unvaccinated residents (2.7% vs 34.4%; RR = 0.0776; estimated effectiveness 92.2%; p = 0.000021). In Vale da Arrancada, coverage was 21/70 (30.0%); no vaccinated resident became a case, compared with 8/49 unvaccinated residents (0% vs 16.3%; p = 0.094870). Overall, infection occurred in 2/96 vaccinated and 19/81 unvaccinated residents (2.1% vs 23.5%; RR = 0.0888; estimated effectiveness 91.1%; p = 0.000009). Vaccination was associated with markedly lower hepatitis A infection. Whole-community outreach achieved substantially higher coverage than reactive household-based vaccination, while non-vaccination concentrated cases in both communities. These findings support early context-adapted vaccination strategies in socially vulnerable settings during hepatitis A outbreaks. Key messages: • Whole-community vaccination in the higher-risk setting achieved greater coverage and was associated with lower hepatitis A infection. • Considering protection only from 14 days after vaccination, cases were concentrated among non-vaccinated residents in both communities.
SN - 1101-1262
SN - 1464-360X
ER -