OBJECTIVE: To compare the impact of three strategies for delivering a booster dose of adult-formulated tetanus-diphtheria-pertussis (Tdap) vaccine to adolescents in Australia.These comprise: (i) administering Tdap to: a one-year age cohort; (ii) administering Tdap to the entire high school and to subsequent entrant cohorts; and (iii) administering Tdap to the entire high school but without continuing to immunize entrant cohorts.METHODS: A series of ecologic analyses of pertussis notifications during epidemic periods in relevant age cohorts were conducted.
The primary outcome measure was L-ARGININE the incidence rate ratio (IRR), calculated by dividing pertussis incidence after the introduction of Tdap delivery programmes by pertussis incidence during the most recent pre-programme epidemic.FINDINGS: During the epidemic period of 2008-2009, the national-level IRR among age cohorts targeted for Tdap was 0.6 (95% confidence interval, CI: 0.
6-0.7), but among other age cohorts it was 1.1 (95% CI: 1.
1-1.2).Only the jurisdiction that implemented strategy 2 (Western Australia) experienced sustained decreases in pertussis notifications in both adolescents and infants under latigo and billet straps 6 months of age (IRR: 0.
4; 95% CI: 0.3-0.6) until 2009.
CONCLUSION: If confirmed by longer experience in Australia and elsewhere, a broad school-based catch-up programme followed by immunization of school entrants may be the optimum strategy for the implementation of adolescent Tdap programmes.