Diphtheria toxoid vaccine effectiveness: A case-control study in Russia

Prior to the completion of this and other studies, low effectiveness of dip htheria toxoid-containing vaccine was suspected to be a major contributing factor to the diphtheria epidemic that began in the Russian Federation in 1 990, A vaccine effectiveness study was done in Moscow by enrolling physicia n-diagnosed cases and 10 control subjects per case. Controls were matched t o cases by age (13 months) and clinic registration. Vaccination history was abstracted from a standardized form for case-patients and from clinic vacc ination records for control subjects. Two hundred seventeen case-patients a nd 2169 matched controls were included in the study. Most controls (92%) ha d received three or more doses of a diphtheria toroid vaccine, compared wit h 72% of case-patients. The vaccine effectiveness for three or more doses w as 97% (95% confidence interval: 94.3-98.4), Low vaccine effectiveness was not a contributing factor to the diphtheria epidemic in the Russian Federat ion. To control and prevent diphtheria epidemics, it is necessary to achiev e and maintain high vaccination coverage with three or more doses of diphth eria toroid among adults and children.