VACCINE PROPHYLAXIS OF Q-FEVER - A FOLLOW-UP-STUDY OF THE EFFICACY OFQ-VAX (CSL) 1985-1990

Objectives: To examine the efficacy of various batches of a formalin-i nactivated whole cell Coxiella burnetii vaccine (Henzerling strain, Ph ase 1 [Q-Vax, CSL]) in the prevention of Q fever among abattoir worker s. Design and setting: The study was a retrospective cohort survey of all employees at three South Australian abattoirs to determine the inc idence of Q fever among vaccinated and unvaccinated employees during t he period 1985 to 1990. Results: There were two cases of Q fever among 2555 vaccinated employees of the three abattoirs, compared with 55 ca ses among 1365 unvaccinated employees. The two Q fever cases in vaccin ated employees were within a few days of vaccination, before immunity had developed, and represented a coincidence of natural infection and vaccination. Protective efficacy was 100%, even with a batch of Q-Vax containing 20 mu g/dose rather than the standard dose of 30 mu g/dose. Conclusions: Vaccination was effective for at least five years, altho ugh it was uncertain whether this was due to the vaccine per se or to a combination of vaccine immunity reinforced by periodic natural expos ure.