Acellular pertussis (whooping cough) vaccines have been developed because they are supposed to be safer and more efficient than the earlier, whole-cell versions.
Children suffered fevers, febrile seizures and even died after being given the whole-cell vaccine and, it seems, all for very little. The whole-cell version has been reported to be just 48 per cent effective in a recent Swedish trial, and just 36 per cent effective in a study carried out in Italy. This means that nearly two-thirds of children given the vaccine were not, after all, protected, and yet still ran the risks of serious adverse reactions.
The problem is that the new acellular variety doesn't seem to be faring much better. Scientists don't understand which one of the three possible components to the vaccine actually works, although most contain the component known as pertussis toxin (PT).
Researcher Gregory Poland from the Mayo Clinic and Foundation in Rochester, Minnesota, explains: 'The minimum protective level of PT antibody is unclear, the clinical relevance of antibody produced by each of the various components is unknown, and disease continues to occur in the presence of high levels of postimmunization PT antibody.'
Possibly because so little is understood about the acellular version, adverse reactions seem as great. A recent study from the Nationwide Multicenter Acellular Pertussis Trial (NMAPT) examined 2189 children given either a version of the acellular vaccine or the whole-cell version. The study found that the rate of serious adverse reactions - death, near-death, seizures, developmental delay and hospital stays - did not differ between the two types of vaccine (The Lancet, January 27,1996).