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.

Assessment of vaccination coverage among adults 30-49 years of age following a mass diphtheria vaccination campaign: Ukraine, April 1995.

Ukraine has been experiencing epidemic diphtheria since 1991. In efforts to control this epidemic, a mass vaccination campaign was held in April 1995. Persons not vaccinated in the previous 3 years were considered eligible for vaccination with tetanus-diphtheria toxoids (Td). Two cluster sample surveys were conducted to determine vaccination coverage achieved. In the urban and rural survey areas, respectively, 628 and 618 persons 30-49 years of age were interviewed. Fifty-nine percent of urban and 58% of rural participants were eligible for vaccination. During the vaccination campaign, 58% (95% confidence interval [95% CI], 47.1-69.2) of eligible persons received Td in the urban area, compared with 92% (95% CI, 89.2-95.3) in the rural area. Apparent barriers to vaccination included misconceptions about the safety, efficacy, and need for booster doses of Td. Future vaccination campaigns should include targeted information and education messages. Mass vaccination campaigns can be successful in vaccinating large numbers of adults; however, in urban areas, additional efforts may be required to achieve levels of coverage adequate to confer herd immunity and interrupt the diphtheria epidemic.

Ukraine, 1992: first assessment of diphtheria vaccine effectiveness during the recent resurgence of diphtheria in the Former Soviet Union.

A case-control study in Ukraine provided the first data on the field effectiveness of Russian-produced vaccine during the 1990 diphtheria resurgence in the former Soviet Union. For each of 262 diphtheria cases <15 years of age who were reported from January through October 1992, 2 controls, matched by age and clinic, were selected. The effectiveness of three doses of diphtheria vaccine was 98.2% (95% confidence interval: 90.3-99.9). Among controls, 84% had received three or more vaccinations by 2 years of age. These results suggest that the following five hypothesized causes of the outbreak appeared unlikely: appearance of a new "mutant" diphtheria strain, low potency of the Russian-produced diphtheria vaccine, inadequate cold chain, poor host immunogenicity due to radiation exposure from Chernobyl, and low routine childhood vaccination coverage. It is concluded that initial priority for scarce resources for controlling this outbreak should be placed on vaccination of persons susceptible to diphtheria (e.g., adults) rather than revaccination of children.