A 6-month-old infant presents with fever, cough, coryza, and conjunctivitis, followed by a maculopapular rash spreading from the head downwards. The mother reports that the child has not received any vaccinations. Which of the following vaccines would have prevented this infection?

Explanation

The clinical presentation of fever, cough, coryza, conjunctivitis (the "3 Cs"), followed by a descending maculopapular rash, is classic for measles (rubeola). Measles is a highly contagious viral infection preventable by the Measles, Mumps, Rubella (MMR) vaccine. The MMR vaccine is typically given as a live attenuated vaccine, with the first dose usually administered around 9-12 months of age. OPV prevents poliomyelitis. Hepatitis B vaccine prevents Hepatitis B infection. Rotavirus vaccine prevents severe rotavirus gastroenteritis.