Vaccine-preventable disease outbreak response — formative SAQs

SAQ 1 (10 marks)

A 6-year-old child presents to the emergency department with four days of fever, cough, coryza and conjunctivitis. This morning a blotchy maculopapular rash appeared behind the ears and is spreading cephalocaudally. The child has never been vaccinated. The child attends a school where several other unvaccinated children have had a similar illness. In the waiting room there are infants and a woman who is 28 weeks pregnant. ^[3]

Question: Outline the immediate and stepwise outbreak response, including the management of the index case, the contact network and the prevention campaign. (10 marks) ^[1]

Model answer

Recognise, isolate and protect the waiting room (2 marks). This is classic measles — the 3 C's with Koplik-spots-equivalent prodrome and a cephalocaudal rash in an unvaccinated child with a school cluster. The single most important immediate act is airborne isolation (negative-pressure where available) and removal of the case from the waiting room, because measles lingers in the air for up to two hours. Identify the exposed waiting-room contacts, especially the pregnant woman and the infants, because they are the high-risk contacts who drive the prophylaxis triage. ^{[3] [1]}

Confirm and notify (2 marks). Confirm with measles IgM on a single serum plus RT-PCR and genotype on a throat/nasopharyngeal swab and urine; the genotype links the case to the school cluster and distinguishes imported from endemic transmission. Notify public health on clinical suspicion — do not wait for confirmation — because notification triggers the contact-tracing and prophylaxis cascade. ^{[1] [2]}

Build and triage the contact list (2 marks). Map the school, childcare, household and waiting-room exposures, and triage every contact by risk: who is pregnant (and at what gestation), who is under 6 to 12 months, and who is immunocompromised. These are the contacts who pay most for delay and who are prioritised for same-day prophylaxis. Document the infectious period — from four days before to four days after the rash — to define who was exposed. ^{[2] [6]}

Deliver post-exposure prophylaxis within the window (2 marks). Offer MMR within 72 hours of exposure to susceptible contacts; give normal human immunoglobulin within 6 days to the high-risk contacts who cannot receive the live vaccine — the pregnant woman, the immunocompromised child, and infants under 6 to 12 months. The window is narrow, so the contact-tracing effort must reach the high-risk contacts first. Exclude cases until four days after the rash and susceptible contacts through the incubation period. ^{[1] [2]}

Prevent — the catch-up campaign (2 marks). Run ring and catch-up vaccination across the affected school and community to lift two-dose coverage back above the herd-immunity threshold of about 95 per cent. The outbreak ends when the susceptible pool is closed, and the campaign is what closes it — as the Amish-community outbreak showed, rapid identification and aggressive vaccination interrupt transmission. Communicate honestly with the community, address vaccine hesitancy respectfully, and document so the programme learns. ^{[7] [11]}