Measles secondary vaccine failure in a childcare setting: an outbreak report.

Abstract: The Sunshine Coast Public Health Unit (SCPHU) identified a measles case in a childcare educator (CE) with secondary vaccine failure (SVF). The CE had been exposed to a confirmed measles case in a hospital emergency department and later developed symptoms including fever, cough, malaise, and a rash. Diagnostic tests confirmed measles virus infection. Sunshine Coast Public Health Unit (SCPHU) implemented control measures including contact tracing, vaccination, post-exposure prophylaxis, and quarantine for susceptible contacts. Out of 372 identified contacts, 72 were identified as susceptible, all of whom were infants and children. Despite the CE having close contact to all susceptible infants and children, no onward transmission occurred. This suggests that SVF cases pose a lower risk of spreading measles compared to immunologically naïve individuals. This report highlights the importance of prioritising immunologically naïve cases in outbreak responses.