A Clinic Weighs a Measles Vaccination Catch-Up Day
A district clinic serving about 12,000 people plans a one-day measles catch-up campaign. Records show 82% of children aged 9 months to 5 years have received one dose; the target for outbreak control is at least 95%. There are 1,400 children in that age band. The clinic has two vaccinators, each able to vaccinate about 25 children per hour over a 6-hour working day, plus 30 minutes of set-up. Vaccine is supplied in 10-dose vials that must be used within 6 hours of opening, and opened vials cannot be returned. The clinic expects that on the day, about 60% of the unvaccinated children will actually attend, along with 15% of already-vaccinated children whose parents are unsure of their status.
1. Calculate the number of unvaccinated children, the clinic's daily vaccination capacity, and whether the campaign can reach the 95% target in one day.
Read the worked answer
Unvaccinated: 18% of 1400 = 0.18 × 1400 = 252 children.
Capacity: each vaccinator works 6 h minus 0.5 h set-up = 5.5 h. At 25 per hour that is 137.5, so about 137 children per vaccinator, or about 275 for two. Capacity is therefore just above the 252 unvaccinated children, but only if attendance is total.
Expected attendance: 60% of 252 ≈ 151 unvaccinated children, plus 15% of the 1148 already vaccinated ≈ 172 children coming for confirmation. Total attendance ≈ 323 children.
This exceeds capacity (≈275). So in one day the clinic cannot see everyone who arrives, and it certainly cannot reach 95% coverage of the whole cohort, because 40% of the unvaccinated (≈101 children) will not attend at all. The 95% target is not achievable in a single day with this design; the campaign needs follow-up days or outreach.
2. The clinic must decide how to open vials. What is the wastage trade-off, and what should the clinic do?
Read the worked answer
Each opened 10-dose vial must be used within 6 hours. If fewer than 10 children are waiting when a vial is opened, the remainder is wasted. With 323 expected attenders over roughly 5.5 hours and two stations, the flow is about 323 / 5.5 ≈ 59 children per hour, or about 29 per station per hour, close to the 25/hour service rate. So queues will build and vials will usually be filled.
The risk is at the start and end of the day, when attendance is thin. The judgement: open the first vials only when at least 8-10 children are queued at a station, and near the end of the day switch to scheduling arrivals so that a final vial is opened only with enough children present. Do not open a vial for one or two latecomers; instead book them for the next session.
The trade-off is explicit: opening early risks wastage of up to 9 doses per vial; opening late risks turning children away. Given that attendance is expected to exceed capacity, the bigger risk is turning children away, so the clinic should prioritise throughput and accept modest wastage at the margins.