Investigation of a measles outbreak in Brondong subdistrict, Lamongan district, Indonesia, 2023

Objective: Lamongan District Health Office received a report of a suspected measles outbreak from a community health centre and two hospitals in Brondong subdistrict, Lamongan district, Indonesia. An outbreak investigation team was deployed to verify the diagnosis and to determine the magnitude of the outbreak. Methods: This retrospective, 1:1 matched case-control study involved 51 suspected or laboratory-confirmed measles cases and 51 controls selected from household contacts and/or playmates within the same village who did not have measles. Data on case characteristics, clinical symptoms, vaccination status, as well as contact and travel histories were collected via interview. Blood specimens were collected from 25 of the children for laboratory confirmation. Univariate and multivariable logistic regression analyses were conducted to investigate risk factors for measles infection. Results: Nineteen of the 51 measles cases (37.3%) were laboratory-confirmed. All 51 cases exhibited fever and rash (100%) and ranged in age from 11 months to 12 years; 29 (56.9%) were female, and 32 (62.7%) were hospitalized. Over half of the cases occurred in Sedayulawas village (31/51, 60.8%), showing a propagated epidemic pattern. The index case was a 2-year-old girl. Transmission predominantly occurred within the same village through household or playmate contacts. Immunization status and contact history were significantly associated with measles infection. Discussion: The measles outbreak was attributed to a decline in immunization coverage, particularly for the second dose of the measles-rubella vaccine. This decrease was driven by multiple factors, including the impact of the COVID-19 pandemic, misconceptions related to religious beliefs, and the long interval between the first and second vaccine doses, which contributed to the patients who were lost to follow-up. Collectively, these factors increased the vulnerability of children to measles infection.