Choosing from Whole Cell and Acellular Pertussis Vaccines-Dilemma for the Developing Countries

Pertussis or whooping cough is a highly infectious , vaccine preventable, acute respiratory tract disease. Historically, it is a disease of infants and children, but recent data reveals pertussis cases from patients of all ages and gender (1). Of particular importance are the cases of atypical, adolescent and adult pertussis, characterized by persistent cough. Both typical as well atypical pertus-sis have been reported from individual as well as outbreaks from highly vaccinated communities of the western world (1,2). DTP vaccine, introduced in 1940s, has been considered as an efficacious vaccine in reducing the burden of all three diseases against that it protects. It consisted of diphtheria and tetanus tox-oids and a cellular component i.e. inactivated cells of Bordetella pertussis. This whole-cell DTP vaccine (DTwP) has been replaced with acellular DTP vaccine (DTaP) consisting of individual antigens of B. pertussis i.e. pertussis toxin, pertactin, fim-briae, adenylate cyclase etc. The action of shift from whole cell pertussis vaccine to acellular vaccine was carried out in 1990s after reports of side effects associated with DTwP vaccines. The newly introduced acellular vaccine was less reactogen-ic and offer protective immunity in first 6 years of life (3). Pertussis has been witnessed as a reemerging infectious disease in over last two decades. Many groups have attempted to find out the reasons behind the increase in reported cases of pertussis disease among vaccinated populations. Apparent reasons behind this resurgence are; waning vaccine-induced immunity, pathogen adaptation to vaccination by changing their antigenic structure , change in etiology (since pertussis-like diseases may be caused by B. parapertussis), and poor vaccine quality. Pertussis vaccines are not meant to protect against B. parapertussis infections (1,2,4,5). There is a shift of pertussis epidemiology from infants and children to adolescent and adult population , which simply indicates waning vaccine-induced immunity among people of these age groups. Nevertheless, one cannot rule out the possibility that enhanced diagnostic facilities and surveillance system may contribute to raising in reported pertussis cases. In both cases, capability of DTaP vaccine remains questionable (1,5,6). Rise in reported pertussis cases began soon after the introduction of acellular pertussis vaccine (DTaP) having B. pertussis antigens instead of whole cells. At the same time, B. pertussis strains undergo selection pressure and adapt to vaccination by changing their antigenic type that is different than the one used in the vaccine manufacture (5). Pertussis cases and outbreaks are being reported from highly vaccinated populations …