Case-control evaluation of an adult diphtheria immunization program in Ukraine

In response to concerns about diphtheria vaccine efficacy, a case-control study was undertaken in Ukraine in 1996 to determine whether those recently immunized were indeed protected from disease, whether multiple doses were more protective, whether contact with children was related to disease, and whether there were detectable differences in protective efficacy between Western and Russian vaccines. In each of the three sites (one rural and two urban), 60 adults with laboratory-confirmed cases of diphtheria were identified from health center records along with 2 adult controls, who were matched to the case by neighborhood. Demographic and vaccination data were gathered from health center records. Using conditional logistic regression to estimate odds ratios, it was determined that cases were more likely to have had no vaccine in the year prior to the index data (odds ratio, 5.0; 95% confidence interval, 2.8-9.0), for a vaccine efficacy of 80%. Two doses gave greater protection, living with children increased disease risk, and no difference was detectable between the Russian and Western vaccines.