Community and Preventive Medicine
Domain 2 - Community and Preventive Medicine
This domain tests population-level reasoning: how prevention programmes are designed, delivered through the MOH system and evaluated.
Core rules
- Leavell and Clark's levels: primordial (population risk-factor avoidance), primary (immunisation, vector control), secondary (screening, early treatment), tertiary (limiting disability, rehabilitation).
- Screening is justified only if it satisfies Wilson and Jungner: important health problem, accepted treatment, adequate facilities, recognisable latent stage, suitable and acceptable test, understood natural history, agreed policy on whom to treat, acceptable cost, continuous case-finding.
- Sri Lanka's EPI: BCG and hepatitis B vaccine at birth; pentavalent (DTP-HepB-Hib) and OPV at 2, 4 and 6 months with IPV in the first year; MR at 9 months and 3 years; JE in endemic districts; Td in pregnancy.
- Notifiable diseases (dengue, leptospirosis, typhoid, measles) must be notified to the MOH - a statutory duty independent of consent.
Worked example. A measles case is notified from an estate sector. Measles R0 is 12–18, so the herd-immunity threshold is 1 − 1/R0 = 92–94%. District MCV1 coverage is 95%, but the estate sits at 85%: the effective reproduction number there is 15 × 0.15 ≈ 2.25, well above 1, so transmission continues. The response is micro-planning to raise coverage in that pocket plus case-based surveillance and ring vaccination - not a blanket district campaign.
Traps
- Quoting sensitivity alone as proof that a screening test is good.
- Confusing incidence with prevalence when evaluating a programme.
- Describing immunisation without cold chain, defaulter tracing and wastage monitoring.
- An outbreak investigation without the sequence: verify the diagnosis, define the case, find cases, describe by time-place-person, hypothesise, test, control.