1. Which single design limitation most threatens valid estimates of sensitivity and representativeness? How would you address it within six weeks?
The most critical design limitation is the system’s reliance on passive surveillance which threatens both sensitivity and representativeness. Health workers may lack training, motivation or time to report every AEFI and some communities may be completely missed.
To address this within six weeks, I would implement a short-term active surveillance pilot in a selection of underrepresented LGAs. This would involve:
a. Assigning trained health workers or community informants to actively seek and report AEFIs weekly,
b. Leveraging existing immunization outreach structures to minimize cost and delay,
c. Comparing reported cases from active sites to passive ones to estimate under-reporting.
2. Using the CDC surveillance attributes, propose one low-cost intervention to increase sensitivity. State the expected trade-offs, and list 2–3 indicators to detect impact from the intervention.
Intervention:
Distribute simple AEFI reporting job aids and provide short refresher training for frontline health workers during routine supervision visits targeting sensitivity.
Expected Trade-Offs:
May lead to an initial increase in reports of mild or unrelated events, reducing specificity that could temporarily burden health workers with additional tasks.
Indicators to Track Impact:
a. AEFI reporting rate per 10,000 vaccine doses that should increase if possible.
b. Proportion of health facilities submitting at least one AEFI report per month.
c. Completeness of AEFI report forms to ensure quality is maintained.
3. For a newly introduced vaccine, should the AEFI case definition be temporarily broadened to maximize early signal detection?
Yes, temporarily broadening the AEFI case definition is appropriate during the early phase of a new vaccine rollout. It increases the likelihood of detecting rare or unexpected adverse events which is critical for public trust and early risk management.