Table 4.
Impact of routine and catch-up herpes zoster vaccination on GP-diagnosed postherpetic neuralgia by time since cohorts were first eligible for vaccination
| Age on Sept 1, 2013, (age when first eligible for vaccination) | Average cumulative uptake* | Expected events† | Observed events | Incidence rate ratio (95% CI)‡ | Expected incidence per 1000 person-years | Incidence reduction per 1000 person-years (95% CI) | Vaccine effectiveness (95% CI)§ | |
|---|---|---|---|---|---|---|---|---|
| Routine cohorts | ||||||||
| First year after vaccine eligibility | 68–70 years (70–71 years) | 46% | 47·8 | 24 | 0·50 (0·34–0·75) | 1·17 | 0·58 (0·82–0·77) | 100% (54–100) |
| Second year after vaccine eligibility | 69–70 years (70–71 years) | 65% | 43·1 | 21 | 0·62 (0·40–0·95) | 1·26 | 0·48 (0·06–0·76) | 59% (8–92) |
| Third year after vaccine eligibility | 70 years (70–71 years) | 70% | 17·3 | 5 | 0·29 (0·12–0·70) | 1·35 | 0·96 (0·41–1·19) | 100% (43–100) |
| All years of the programme | 68–70 years (70–71 years) | 56% | 99·1 | 50 | 0·50 (0·38–0·67) | 1·23 | 0·61 (0·41–0·76) | 88% (59–100) |
| Catch-up cohorts | ||||||||
| First year after vaccine eligibility | 76–79 years (78–80 years) | 46% | 63·0 | 38 | 0·60 (0·44–0·83) | 1·82 | 0·83 (0·31–1·02) | 86% (37–100) |
| Second year after vaccine eligibility | 77–79 years (78–80) | 62% | 47·1 | 31 | 0·66 (0·46–0·94) | 1·91 | 0·64 (0·11–1·03) | 55% (10–87) |
| Third year after vaccine eligibility | 79 years (79–80 years) | 60% | 15·0 | 9 | 0·60 (0·31–1·16) | 1·99 | 0·80 (−0·32–1·37) | 66% (27–100) |
| All years of the programme | 76–79 years (78–80 years) | 54% | 125·1 | 78 | 0·62 (0·50–0·79) | 1·88 | 0·68 (0·39–0·94) | 70% (39–93) |
Impact is shown by the incidence rate ratio (observed/expected events) and incidence reduction. GP=general practitioner.
*
Calculated by taking the mean of the cumulative uptake values in each month from October to September of the relevant years and cohorts.
†
Expected if the vaccine had not been introduced; based on model results for unvaccinated cohorts.
‡
Estimated from the Poisson regression model with a log-linear time trend, quadratic age effect, and the factor for vaccine eligibility.
§
Effectiveness required to generate the observed reductions in the first 3 years after vaccination.