Two vaccine-associated measles cases: Transmission or coincidental cases?

Measles, a highly contagious airborne disease, has seen a resurgence in Spain despite the successful implementation of vaccination programs. This study examines two cases of vaccine-associated measles in children attending the same nursery school, both of whom received the measles-mumps-rubella vaccine.

Retrospective descriptive study of two children with vaccine-associated measles in May 2025 on the island of Gran Canaria (Spain).

The first case involved a 12-month-old girl who developed symptoms six days post-vaccination, while the second case, a 13-month-old boy, exhibited symptoms eight days after receiving the vaccine. Both cases were confirmed as genotype A, indicating the vaccine strain. The investigation included extensive contact tracing, identifying 107 close contacts, with vaccinations administered to susceptible individuals. Laboratory tests confirmed measles through polymerase chain reaction (PCR) analysis. The findings highlight the rarity of clinically significant vaccine-associated disease and the absence of evidence for human-to-human transmission of the vaccine strain.

This study underscores the importance of genotyping in distinguishing between vaccine-associated rash illness and wild-type measles, as well as the need for continued vigilance in monitoring vaccine efficacy and outbreak responses. Ultimately, while the possibility of transmission cannot be entirely dismissed, the evidence suggests that these cases are more likely coincidental rather than a result of transmission.