Re-emergence of diphtheria and pertussis: implications for Nigeria.

In the prevaccine era pertussis and diphtheria were responsible for significant morbidity and mortality in children. In the United States of America more than 125,000 cases of diphtheria with 10,000 deaths were reported annually in the 1920s. In the same period about 1.7 million cases of pertussis with 73,000 deaths were also reported. Vaccination against these two diseases has caused remarkable reduction in the morbidity and mortality from these diseases both in developed and developing countries. The initial vaccines were the combined diphtheria toxoid and whole cell pertussis vaccine. The recent reported increases in the incidence of these two diseases in countries, which maintain high childhood vaccination coverage is a source of concern not only to these countries but also for developing countries with weak immunization programmes. Nigeria for example reported 11,281 cases of pertussis, the second highest number of cases worldwide in 2009. Waning immunity in adult and adolescent populations has been reported and epidemiologically, more cases are being reported in adults and adolescents. Also a high proportion of pertussis cases are being reported in infants and most of these infant cases are linked to adult/adolescent sources. Recent approaches to control of these diseases include booster doses of combined diphtheria, tetanus and acellular pertussis vaccine while the cocooning strategy (which is immunizing every person who is likely to have contact with a given infant such as mother, father, grandparents and health care workers) is being used in a number of countries. For developing countries including Nigeria where the capacity for making the diagnosis of both diseases is limited, strengthening of routine immunization as well as diagnostic capacity is imperative. Research to determine current levels of immunity in children, adolescents and adults is required. This will enable the determination of the need for booster doses and the age at which such boosters should be administered. Improved surveillance will be needed to delineate current epidemiological profiles of both diseases.