RESUMO
INTRODUCTION: During the last decade, measles has become an important re-emerging disease in Thailand. The objective of this study was to measure measles seroprevalence and its influencing factors and to plan for an improved vaccination program. METHODS: A total of 600 participants aged between 9 months and 50 years were divided into seven groups those represent birth cohorts that experienced different measles vaccination policies. Participants' blood samples were obtained to measure measles immunoglobulin G (IgG) levels. RESULTS: None of the participants in the 9-month age group had measles IgG levels beyond a protective level. Participants in the following age groups: 2 ½, 5-15, 16-29, 30-33, 34-40, and 41-50 years had 82% (95% confidence interval [CI] 73.3-90.7), 50% (95% CI 36.1-63.9), 52% (95% CI 42.3-62.7), 70% (95% CI 61.1-78.9), 88.8% (95% CI 84.1-93.5), and 98.8% (95% CI 96.4-100.0) measles seropositivity, respectively. The study did not find any significant factors affecting measles seropositivity. CONCLUSION: Individuals aged 15-34 years are vulnerable to measles infections. Supplementary vaccination in special situations, including post-exposure prophylaxis during an outbreak among young adults or providing for high-risk occupations, such as healthcare personnel, should be encouraged.