Recommendations for UseDTaP vaccines are not more efficacious than DTwP vaccines, they have fewer adverse effects. It must also be remembered that serious adverse effects are rare phenomena even with the whole cell vaccine unlike popular belief. The IAPCOI therefore unequivocally endorses the continued use of DTwP vaccine in EPI because of its low cost, proven efficacy and safty. The use of DTaP vaccine in office practice should be following one to one discussion with parents on a named child basis (Category 3). The DTaP vaccines may be preferred to DTwP vaccines in those children with history of severe adverse effects following DTwP vaccines or children with neurologic disorders if resources permit. The schedule is same as with DTwP vaccines. Like DTwP vaccines, DTaP vaccines must not be used in children 7 years or older because of increased reactogenicity. All licensed DTaP vaccines are of similar efficacy and safety as of currently available data and any one of them may be used. DTaP combination vaccines will be discussed separately. |
|
|
The introduction of the whole cell vaccines paid rich dividends in terms of decline in disease morbidity and mortality. Once disease rates declined, concern over minor, serious and “devastating” adverse effects of the pertussis component of the whole cell vaccines led to development of the acellular pertussis vaccines in Japan in 1981. These were licensed in the US in 1996 and have now replaced the whole cell vaccines in many developed countries.
The components of pertussis bacilli used for preparation of the acellular vaccines include pertussis toxin (PT) as the essential component with or without filamentous hemagglutinin (FHA), pertactin (PRN) and fimbrial hemagglutinins 1, 2 and 3 (FIM). Commercially available vaccines vary in number of components, quantity of components and method of inactivation of the components. Currently available aP vaccines in India include five component vaccines (Tripacel TM- PT, PRN, FHA, FIM 2 and 3), three component vaccines (Infanrix TM - PT, FHA, PRN) and a two component combination vaccine (PentaximTM - PT and FHA, IPV, Hib).
The vaccines should be stored at 2 to 8°C and the recommended dose is 0.5 ml intramuscularly. The efficacy and duration of protection with DTaP vaccines against diphtheria/tetanus and pertussis is similar to that afforded by the whole cell vaccines. There is considerable controversy on the relative efficacy of different acellular vaccines with varying number of components. The efficacy is influenced not only by number of components but also by quantity of antigen and method of inactivation. Even monocomponent vaccines with only PT have performed well in national programs. Review of clinical trial data and experience from field use in national programs indicates that all currently licensed acellular pertussis vaccines have similar efficacy. All DTaP vaccines show better efficacy against severe disease than mild disease.
The DTaP vaccines score over the whole cell vaccines in
terms of adverse effects. Broadly speaking the incidence of
both minor and major adverse effects is reduced by two thirds
with the acellular vaccines. The incidence of adverse effects is
similar with all currently licensed DTaP vaccines. The absolute
contraindications to DTaP vaccines are same as those for whole
cell vaccines and include history of anaphylaxis/encephalopathy
following past pertussis vaccination. Serious adverse events
following previous pertussis vaccination (listed in DTwP
section) though less likely as compared to DTwP may still
occur with DTaP and are similarly considered as precautions
while using the vaccine.