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Measles exposure in an infant — MSRA MCQ

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HardInfectious DiseasesMeasles exposure in an infantMSRA

A 7-month-old infant is brought to general practice after her mother is diagnosed with PCR-confirmed measles. The mother’s rash began 4 days ago. The infant had close household contact with her throughout the mother’s prodromal illness and for the first 3 days of the rash; the mother was admitted to hospital yesterday. The infant is well and has not received any measles-containing vaccine. What is the most appropriate post-exposure management today?

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Correct answer: E — Arrange human normal immunoglobulin (HNIG) today via the local health protection pathway

This infant requires HNIG today. She is aged 6–8 months and had household exposure, which is treated as a high-intensity exposure. UKHSA recommends HNIG for infants of this age after household exposure, ideally within 72 hours but up to 6 days if necessary. For household contacts, the post-exposure prophylaxis window is calculated from rash onset in the index case, rather than from the last contact, because exposure is usually ongoing during the relevant period. At day 4 after maternal rash onset, HNIG remains indicated. MMR is appropriate for 6–8-month-olds exposed outside the household, where exposure intensity is usually lower; it is not the recommended prophylaxis in this household scenario. MMRV is not licensed in this age group. Measles IgG testing is not required before prophylaxis in this age- and exposure-defined infant group. Safety-netting alone would be inadequate because the HNIG window remains open; although effectiveness is greatest early, HNIG can still be used up to 6 days after exposure to reduce the risk or severity of disease.

Reference: National measles guidelines (30 July 2026) — https://assets.publishing.service.gov.uk/media/69cbc91fa60a12ca3913c644/ukhsa-national-measles-guidelines-version-7-march-2026.pdf National measles guidelines (30 July 2026) — https://assets.publishing.service.gov.uk/media/69cbc91fa60a12ca3913c644/ukhsa-national-measles-guidelines-version-7-march-2026.pdf National measles guidelines (30 July 2026) — https://assets.publishing.service.gov.uk/media/69cbc91fa60a12ca3913c644/ukhsa-national-measles-guidelines-version-7-march-2026.pdf