Single-dose varicella vaccine effectiveness in Brazil: a case-control study
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2018
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Background: Varicella vaccine was introduced into the Brazilian Immunization Program in October 2013,
as a single-dose schedule administered at 15 months of age. Its effectiveness had not yet been assessed in
the country.
Methods: A matched case-control study was carried out in São Paulo and Goiânia (Southeast and Midwest
regions, respectively), Brazil. Suspected cases, were identified through a prospective surveillance estab lished in the study sites. All cases had specimens from skin lesion collected for molecular laboratory test ing. Cases were confirmed by either clinical or PCR of skin lesions and classified as mild, moderate, and
severe disease.
Methods: Two neighborhood controls were selected for each case. Cases and controls were aged 15–32
months and interviewed at home. Evidence of prior vaccination was obtained from vaccination cards.
Univariate and multivariate logistic regression models were used, and odds ratio and its respective
95% confidence intervals were estimated. Vaccine effectiveness was estimated by comparing de odds
of having received varicella vaccine among cases and controls.
Results: A total of 168 cases and 301 controls were enrolled. Moderate and severe illness, was found in
33.3% and 9.9% of the cases. Effectiveness of a single dose varicella vaccine was 86% (95%CI 72–92%)
against disease of any severity and 93% (95%CI 82–97%) against moderate and severe disease. Out of
168 cases, 81.8% had positive PCR results for wild-type strains, and 22.0% were breakthrough varicella
cases. Breakthrough cases were milder compared to non-breakthrough cases (p < .001).
Conclusions: Effectiveness of single dose varicella vaccine in Brazil is comparable to that in other coun tries where breakthrough varicella cases have also been found to occur. The goal of the varicella vaccina tion program, along with disease burden and affordability should be taken into consideration when
considering the adoption of a second dose of varicella vaccine into national immunization programs.
2017 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND
license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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Palavras-chave
Varicella vaccination, Breakthrough, Universal routine vaccination, Vaccine effectiveness
Citação
ANDRADE, Ana Lucia et al. Single-dose varicella vaccine effectiveness in Brazil: a case-control study. Vaccine, Amsterdam, v. 36, n. 4, p. 479-483, 2018. DOI: 10.1016/j.vaccine.2017.12.011. Disponível em: https://www.sciencedirect.com/science/article/pii/S0264410X17317516?via%3Dihub. Acesso em: 12 ago. 2024.