Investigation of a measles outbreak on Phu Quoc Island, Viet Nam, April–June 2024
DOI:
https://doi.org/10.5365/wpsar.2026.17.3.1397Keywords:
measles, outbreak investigation, surveillance, vaccination coverage, VietnamAbstract
Objective: In 2024, following detection of a measles outbreak on Phu Quoc Island, Viet Nam, an investigation was conducted to describe the epidemiological characteristics and assess response timeliness using the 7-1-7 framework.
Methods: Suspected measles cases were identified through syndromic surveillance (those with fever and rash, plus respiratory inflammation and/or conjunctivitis) and confirmed by serological testing. Demographic and epidemiological information was collected with standardized questionnaires. Vaccination status was verified using the National Immunization Information System and personal vaccination records, with full vaccination defined as two doses of measles-containing vaccine. The 7-1-7 framework was used to assess timeliness of detection (7 days), notification (1 day) and response (7 days).
Results: Of 137 suspected measles cases occurring between 7 April and 7 June 2024, 83 (60.6%) were confirmed. Cases occurred mainly among school-aged children (6–10 years, n = 55; 40.1%), with schools as the primary exposure setting (n = 56; 40.9%). Among the 55 school-aged children, 10 (18.2%) were fully vaccinated. The attack rate was significantly higher among school-aged children who had not received two vaccine doses than among those who were fully vaccinated (0.9% [45/4988] vs 0.1% [10/8917], P < 0.001). Outbreak detection was delayed by 15 days, notification occurred within 1 day of identification of the first suspected case, and response was within 5 days of notification.
Discussion: This outbreak was likely caused by gaps in vaccination coverage and delayed recognition of early warning signs. Strengthening immunization, early case detection and reporting systems are essential to prevent future outbreaks.
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Copyright (c) 2026 Pham Nguyen Phu Khanh, Tran The Vinh, Vo Thi Thuy Tram, Bui Trung Nghia, Le Hoang Phuong, Nguyen Ngoc Bao Chau
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