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A resurgence of diphtheria spread throughout the Russian Federation in the early 1990s; diphtheria had been well controlled, but circulation of toxigenic strains of Corynebacterium diphtheriae had persisted since the implementation of universal childhood vaccination in the late 1950s. More than 115,000 cases and 3,000 deaths were reported from 1990 to 1997, and, in contrast to the situation in the prevaccine era, most of the cases and deaths occurred among adults. Contributing factors included the accumulation of susceptible individuals among both adults and children and probably the introduction of new strains of C. diphtheriae. Vaccine quality, vaccine supply, or access to vaccine providers did not significantly contribute to the epidemic. Mass vaccination of adults and improved childhood immunization controlled the epidemic. High levels of population immunity, especially among children, will be needed to prevent and control similar outbreaks in the future.

Background: Between 1990 and 1996, more than 110,000 cases and 2900 deaths from diphtheria were reported in the Russian Federation. In 1994, because disease rates were high among children aged 7-10 years, the age of administration of the second booster dose of diphtheria vaccine was lowered from 9 years to 6 years, the age of school entry. To assess the impact of this policy change, we did a matched case-control study in three Russian cities., Methods: Children aged 6-8 years who had diphtheria between September, 1994, and December, 1996, were each matched with five to seven children acting as controls who were within 3 months of age of the case and were from the same class at school. We did a matched analysis using conditional logistic regression., Findings: We analysed the immunisation records of 58 cases and 306 controls. All but one case and all controls had received at least three doses of diphtheria-toxoid vaccine. 19 (33%) cases and 144 (47%) controls had received a booster dose of diphtheria toxoid within the previous 2 years. Cases were more likely than were controls to have received only four doses rather than five (odds ratio 2.8 [95% CI 1.2-6.5]) and to have a time since the last dose of diphtheria toxoid of 3-4 years (3.1 [1.1-9.1]) or 5-7 years (15.0 [2.5-89.0]), compared with children for whom it was 2 years or less. On multivariate analysis only a time since the last dose of 5-7 years remained significantly associated with disease (matched odds ratio adjusted for total number of doses 10.9 [1.6-75.1])., Conclusion: A booster dose of diphtheria-toxoid vaccine given to children in the Russian Federation at 6-8 years of age reduced the interval since the last dose of diphtheria toxoid and improved protection against diphtheria.

Background: A massive diphtheria epidemic which began in the former Soviet Union in 1990 is the first large-scale diphtheria epidemic in developed countries in more than 30 years and has primarily affected adults. In response, health authorities attempted to maximize vaccination for children and conducted an unprecedented campaign to vaccinate adults., Methods: We analyzed diphtheria surveillance data (case report forms and diphtheria vaccine coverage data) from three Russian regions from January 1994 to December 1996 and estimated vaccine effectiveness by the screening method., Results: We reviewed records from 2243 (97.2%) of 2307 reported cases. The highest cumulative incidence in the period was among children aged 5 to 9 years (106 cases per 100,000 population); adults aged 40-49 years had the highest adult incidence for disease (88 cases per 100,000) and the highest incidence of any age group of clinically severe disease (29 cases per 100,000) and death (5.1 deaths per 100,000). The incidence among women aged 2049 years (82 per 100,000 women) was higher than among men (47 per 100,000, p<0.01). The annual incidence decreased from 25.2 cases per 100,000 population in 1994 to 9.4 cases per 100,000 in 1996. The decrease occurred as adult coverage increased from an estimated 25-30% in December 1992 to 88% in December 1995. Vaccine effectiveness was high among both children and adults., Conclusions: The Russian diphtheria epidemic primarily affected adults, especially women; this pattern is likely representative of diphtheria epidemics in immunized populations. Raising childhood immunization coverage and mass adult vaccination was effective in controlling the Russian epidemic. An improved understanding of the current epidemiology of diphtheria will be useful to design public health responses to prevent or control modern epidemics.