Single-dose varicella vaccine effectiveness in Brazil: A case-control study
Ana Lucia Andrade1, Maria Aparecida da Silva Vieira2, Ruth Minamisava3
1Institute of Tropical Pathology and Public Health, Federal University of Goias, Brazil.
Vaccine
|December 19, 2017
Summary
The single-dose varicella vaccine in Brazil is 86% effective against chickenpox. Breakthrough cases were milder, suggesting vaccine effectiveness comparable to international standards.
Area of Science:
- Immunology
- Epidemiology
- Public Health
Background:
- The varicella vaccine was integrated into Brazil's national immunization program in October 2013, utilizing a single-dose schedule for children aged 15 months.
- The vaccine's effectiveness within the Brazilian context had not yet been evaluated.
Purpose of the Study:
- To assess the effectiveness of the single-dose varicella vaccine in Brazil.
- To analyze the characteristics of varicella cases and breakthrough infections.
Main Methods:
- A matched case-control study was conducted in São Paulo and Goiânia, Brazil.
- Cases were identified through prospective surveillance and confirmed via clinical or PCR testing.
- Vaccine effectiveness was calculated using logistic regression models comparing vaccination status between cases and controls.
Main Results:
- The study included 168 cases and 301 controls, with 33.3% experiencing moderate and 9.9% severe illness.
- Single-dose varicella vaccine demonstrated 86% effectiveness against any varicella disease severity and 93% against moderate to severe disease.
- Breakthrough varicella cases (22.0%) were milder than non-breakthrough cases (p < .001).
Conclusions:
- The single-dose varicella vaccine exhibits significant effectiveness in Brazil, aligning with international findings.
- The occurrence of milder breakthrough varicella cases warrants consideration of program goals, disease burden, and cost-effectiveness when evaluating a potential second vaccine dose.
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