Background. Unexpected waning of immunity after pertussis vaccination is now well described. In this study we examined whether prior vaccination with whole-cell pertussis vaccine (wP) at any point provided superior protection contrasted with a solely acellular pertussis vaccine (aP) series. We utilized the coincidence of a large outbreak of pertussis with the termination of wP availability, providing populations of children who had been vaccinated with combinations of wP and aP.
Methods. Kaiser Permanente (KP) is an integrated healthcare system with complete electronic records and a centralized laboratory. Cases of laboratory-confirmed pertussis and vaccination data for members aged 8–20 years were retrieved.
Results. Among 263 496 persons aged 8–20 years, 904 cases of pertussis were identified. In patients with a full history of vaccinations administered by KP, those with 5 total doses of only aP had an 8.57 relative risk (RR) of pertussis (P < .0001) contrasted to those with ≥1 wP dose. With 6 doses of aP, the RR of disease was 3.55 (P < .0001). When external vaccine records were included, the results were similar.
Conclusions. We found a markedly increased risk of disease associated with an entirely aP series. This risk was mitigated, but not eliminated, by the presence of a sixth dose of pertussis vaccine (Tdap). Receipt of 1 or more wP doses markedly augmented the durability of immunity from subsequent aP doses. It appears that a wholly acellular pertussis vaccine series is significantly less effective and durable than one that contains the traditional whole cell vaccine.
Comment: There have been epidemics of Pertussis (whooping cough (Kaali khaansi in Hindi) in US, UK & Australia in the last year. Research is increasingly implicating the use of DTaP as a causative factor in this situation. Given that most private practitioners in larger Indian cities are providing (the much more expensive) DTaP to our customers, I believe that the time has introspect, and recommend at least 1 dose of DTwP for all kids in our follow up. As per theoretical models, the first dose of DPT vaccine may be DTwP, followed by DTaP for affording parents to reduce the chances of side-effects, without compromising the efficacy.