Explaining measles isolation, prophylaxis and catch-up vaccination — OSCE

Candidate instructions (8-minute station)

You are the paediatric registrar in the clinic. A 6-year-old child who has never been vaccinated has four days of fever, cough, coryza and conjunctivitis, and today a blotchy rash spreading from behind the ears downward. You suspect measles and have sent IgM and PCR. Several unvaccinated schoolmates have a similar illness. At home there is a 10-week-old infant sibling, and the child's aunt, who is 28 weeks pregnant, visits daily. [3]

Your tasks are: [1]

1. Explain the suspected diagnosis of measles and what the illness and its complications look like, in plain language. [3]
2. Explain the airborne isolation and exclusion plan — why the child must stay home until four days after the rash — and why it matters even though the child may be improving. [1]
3. Explain why the 10-week-old infant sibling and the 28-weeks-pregnant aunt need same-day assessment and prophylaxis within the window, and what that involves. [2]
4. Explain why the unvaccinated schoolmates need MMR within 72 hours, and how the catch-up vaccination campaign that lifts coverage above the herd-immunity threshold prevents the next outbreak. [11]

You are not expected to take the full contact-tracing history yourself or to prescribe immunoglobulin doses without senior review — flag that the infant and the pregnant aunt need same-day assessment. [2]

Examiner prompt to the actor (parent)

"But he's getting better already — does he really have to stay home? And you're telling me the baby and my pregnant sister need some kind of injection today? They're not even sick. And why are you talking about vaccinating the whole school — isn't that their business?" [2]

Marking domains

• Frame and explanation (3): explains measles and its contagiousness and complications (pneumonia, encephalitis) in plain, honest language; names that the child may improve but remains infectious; sets the expectation that this is a community problem, not just this child's illness. [3]
• Isolation and exclusion plan (3): explains clearly that the child must stay home, away from other children and especially the baby, until four days after the rash appeared, because measles spreads in the air for hours and the child is most infectious before and during the early rash; explains that measles is notifiable and that public health will be involved. [1]
• Protecting the high-risk contacts (3): explains that the 10-week-old infant (too young to be fully vaccinated) and the 28-weeks-pregnant aunt are exactly the contacts who need same-day assessment and prophylaxis — immunoglobulin within six days, because they cannot simply rely on the vaccine — because measles in an infant and in pregnancy carries real harm; frames the aunt's pregnancy as the reason for urgency. [2]
• Prevention and the catch-up campaign (1): explains that the unvaccinated schoolmates need MMR within 72 hours to prevent or modify disease, and that the school catch-up campaign is what ends the outbreak by lifting coverage above the herd-immunity threshold — protecting the next pregnant woman and infant at the edge of the outbreak. [11] [6]

Model answer — the explanatory script

"Thank you for bringing him in. I'm concerned this is measles. The pattern — the fever, the cough, the runny nose and red eyes for a few days, and now this rash starting behind the ears and moving down — is very typical, especially in a child who hasn't had the measles vaccine. I've sent a test to confirm, but I want to act now rather than wait." [3]

"Measles is the most contagious infection we know — it spreads through the air, and it can linger in a room for a couple of hours after someone with it has left. For most children it's a rough week or two, with fever and rash, and then they recover. But it can cause pneumonia, and more rarely inflammation of the brain, so we take it seriously. The good news is your son is already past the worst of the prodrome, but here's the important part — he's still infectious." [3]

"So, staying home. He needs to stay home, and away from other children — especially the baby — until four full days after the rash first appeared. That's the point at which he's no longer contagious. It's not about how well he feels now; it's about not passing it to someone it could really hurt. Measles is a notifiable illness, which means our public-health team will be in touch to help map who he's been in contact with." [1]

"Now, the most important part — your baby and your sister. Your baby is only ten weeks old, which means he's too young to be fully protected by vaccination yet. Measles in a tiny baby can be very serious. And your sister, being 28 weeks pregnant — measles in pregnancy carries real risks for her and the pregnancy. Because they can't simply rely on the vaccine the way an older child can, we want to give them a protective injection called immunoglobulin, and it works best if it's given within six days of the exposure. That's why I want them both assessed today, not next week. We're not waiting because they're sick — we're acting because the window to protect them is now." [2]

"And finally, the school. Every unvaccinated classmate who was around your son is now a contact. If they get the measles vaccine within 72 hours of the exposure, it can actually prevent the illness or make it much milder. So public health will be working with the school to offer that. The bigger picture is this: measles comes back whenever vaccination coverage in a community dips below about 95 per cent. The way we end this outbreak and prevent the next one is to get that coverage back up — so that the next pregnant woman, and the next baby, at the edge of an outbreak are protected before the virus ever reaches them." [11] [6]