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RSV prevention in a subsequent pregnancy — ABIM Board MCQ

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HardACIPRSV prevention in a subsequent pregnancyABIM Board

A 33-year-old woman at 34 2/7 weeks’ gestation is seen in Illinois during December. Her pregnancy has been uncomplicated, and delivery is expected in January. During a previous pregnancy 2 years ago, she received the Pfizer RSVpreF vaccine (Abrysvo) at 34 weeks’ gestation. Her child from that pregnancy is healthy. She has no immunocompromising condition, and the current fetus has no identified condition associated with increased risk of severe respiratory syncytial virus disease. She asks whether another dose is needed to protect this infant. Which of the following is the most appropriate RSV prevention strategy?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Withhold maternal RSV vaccine and administer a long-acting RSV monoclonal antibody to the infant within 1 week after birth

Explanation lettering: E = shown as A · D = shown as B · A = shown as D · B = shown as E

Although this patient is within both the recommended gestational window (32 0/7–36 6/7 weeks) and the usual September–January seasonal window, CDC does not currently recommend repeating maternal RSV vaccination in a subsequent pregnancy after a dose given during any previous pregnancy. Because she has not been vaccinated during the current pregnancy, her newborn should receive a long-acting RSV monoclonal antibody, either nirsevimab or clesrovimab. An eligible infant born during October–March should receive it within 1 week after birth, ideally during the birth hospitalization. B would be appropriate for an otherwise eligible patient who had never received maternal RSV vaccine; infant antibody is generally unnecessary when birth occurs at least 14 days after vaccination. C incorrectly repeats the maternal dose and provides both products despite no rare circumstance warranting additive protection. D is incorrect because postpartum maternal vaccination is not recommended as a method of protecting the newborn through breast milk. E delays prophylaxis during the infant’s period of immediate RSV exposure; the recommended timing for a January birth is within the first week of life, not at the routine 2-month visit.

Reference: RSV Vaccine Guidance for Pregnant Women (August 30, 2024) — https://www.cdc.gov/rsv/hcp/vaccine-clinical-guidance/pregnant-people.html RSV Immunization Guidance for Infants and Young Children (August 18, 2025) — https://www.cdc.gov/rsv/hcp/vaccine-clinical-guidance/infants-young-children.html