Following the introduction of routine immunization with diphtheria toxoid in the 1940s and 1950s, diphtheria incidence declined dramatically in countries of the industrialized world. At the beginning of the 1980s many of these countries were progressing toward elimination of the disease. However, since the mid-1980s there has been a striking resurgence of diphtheria in several countries of Eastern Europe. For 1993, WHO received reports of 15,211 diphtheria cases in Russia and 2,987 cases in Ukraine. The main reasons for the return of diphtheria in these countries were: decreasing immunization coverage among infants and children waning immunity to diphtheria in adults, movements of the population during the last few years, and an irregular supply of vaccines. The outbreak spread to neighboring countries and in 1993 cases were reported in Azerbaijan, Belarus, Estonia, Finland, Kazakhstan, Latvia, Lithuania, Poland, Tajikistan, Turkey, and Uzbekistan. Epidemiological patterns of diphtheria are changing in developing countries, and the disease seems to be following patterns seen in industrialized countries 30 to 40 years ago. In developing countries, routine immunization against diphtheria was introduced in the late 1970s with the Expanded Programme on Immunization. In these countries, coverage of infants with 3 doses of diphtheria toxoid reached 46% in 1985, and 79% in 1992. Recent diphtheria outbreaks in Algeria, China, Ecuator, Jordan, Lesotho and Sudan demonstrate a shift in the age distribution of cases to older children and adults. Rapid clinical and public health responses are required to control diphtheria outbreaks. Three major measures are indicated: high immunization coverage of target groups, prompt diagnosis and management of diphtheria cases, and rapid identification of close contacts with their effective management to prevent secondary cases.

After >10 years without detection of any cases of wild virus-associated poliomyelitis, a large outbreak of poliomyelitis occurred in Albania in 1996. A total of 138 paralytic cases occurred, of which 16 (12%) were fatal. The outbreak was due to wild poliovirus type 1, isolated from 69 cases. An attack rate of 10 per 100,000 population was observed among adults aged 19-25 years who were born during a time of declining wild poliovirus circulation and had been vaccinated with two doses of monovalent oral poliovirus vaccines (OPVs) that may have been exposed to ambient temperatures for prolonged periods. Control of the epidemic was achieved by two rounds of mass vaccination with trivalent oral poliovirus vaccine targeted to persons aged 0-50 years. This outbreak underscores the ongoing threat of importation of wild poliovirus into European countries, the importance of delivering potent vaccine through an adequate cold chain, and the effectiveness of national OPV mass vaccination campaigns for outbreak control.