A 30-Year-Old Male Pediatrician With Documented Complete Vaccination History and Laboratory-Confirmed Breakthrough Measles With Respiratory Involvement During a Measles Outbreak in Mexico

Symptoms:Fever and a cephalocaudal maculopapular rash, followed by progressive systemic and respiratory symptoms, including cough, pharyngitis, and mild pain on breathing Clinical Procedure:-Specialty: Public Health Background:The global resurgence of measles has been accompanied by reports of breakthrough infection in previously immunized individuals, including healthcare personnel.Breakthrough measles can present with attenuated or atypical findings, but the clinical spectrum in fully vaccinated adults remains incompletely characterized.During outbreaks, documenting laboratory-confirmed cases in vaccinated healthcare workers is clinically relevant. Case Report:We describe a 30-year-old male pediatrician with a fully vaccinated history for measles, including 2 childhood doses and a measles-rubella booster in 2017, who developed measles after occupational exposure to an unvaccinated 6-year-old patient.Six days after exposure, he developed fever and a cephalocaudal maculopapular rash, followed by progressive systemic and respiratory symptoms, including cough, pharyngitis, and mild pain on breathing.On day 9, a room-air oxygen saturation of 92% prompted brief supplemental oxygen and short inpatient observation.Chest auscultation was normal, and thus chest radiography was not performed.Oxygenation improved rapidly with supportive care.Measles virus RNA was detected by real-time reverse-transcription polymerase chain reaction in a pharyngeal swab.He received supportive care, was hospitalized for 2 days, and recovered fully after 2 weeks of follow-up, with no documented complications or secondary cases among monitored contacts. Conclusions:This case provides a descriptive, laboratory-confirmed example of breakthrough measles in a fully vaccinated healthcare worker during an active outbreak.Although these observations are consistent with partial or waning immunity, the exact mechanism of vaccine failure could not be established because pre-exposure measles serology and viral genotyping were not performed.Serological surveillance or targeted booster strategies for healthcare personnel should be regarded as context-dependent considerations requiring support from broader epidemiologic and serologic evidence.