A randomized, controlled, double-blind, cross-over, clinical trial of Q fever vaccine in selected Queensland abattoirs.

A limited, randomized, blind, placebo-controlled trial of Q fever and influenza vaccines has been conducted in three Queensland abattoirs on a sequential analysis design. Ninety-eight subjects were given Q fever vaccine and 102 influenza vaccine. Q fever cases were observed in unvaccinated workers in all three abattoirs during the period of observation. A total of seven Q fever cases in one group, one more than the number required to achieve statistical significance between the two vaccine groups, was reached after 15 months with the cases coming from two of the abattoirs. These Q fever cases were in the group which had been given influenza vaccine and none in that given Q fever vaccine. Symptomless seroconversion rates of 24% were found in the remaining influenza virus vaccinees, and those without immunity were given Q fever vaccine.