4 February 2011
New acellular vaccines may be contributing to the current whooping cough (pertussis) epidemic, according to new data from the Cochrane Collaboration, an international organisation that undertakes scientific reviews of evidence for certain treatments.
Reviewers confirmed acellular pertussis vaccines were less effective than whole-cell vaccines, which have been discontinued in Australia.
Combined results from 6 efficacy and 52 safety trials showed multicomponent acellular vaccines were more effective than low efficacy whole-cell vaccines, but may be less effective than the highest-efficacy whole-cell vaccines. However, acellular pertussis vaccines have fewer side effects than whole-cell vaccines (Cochrane Database of Systematic Reviews 2011; 1: CD001478).
Professor Peter McIntyre, director of the National Centre for Immunisation Research and Surveillance, Sydney, said it was possible the acellular vaccines were contributing to the high numbers of whooping cough cases in Australia, although the wider availability of PCR testing meant more cases were being identified. (PCR, or polymerase chain reaction, is more sensitive for identifying cases than older tests as it detects bacterial DNA.)
"One aspect that seems to be emerging with acellular vaccines compared to whole-cell [vaccines] is the duration of immunity may be lower", he said.
The removal of the 18-month booster dose could also be contributing to the epidemic, and the Australian Technical Advisory Group on Immunisation was considering whether it should be reinstated on the vaccination schedule, he said.
Acellular vaccines appeared to be associated with less severe disease, he said.
"We had the big epidemic, 1997 to 1999 in the whole-cell era; across the country there were 9 deaths", he said.
"Over a comparable period in this epidemic, using acellular vaccines, we’ve had 4 deaths."
The Cochrane review found that multicomponent acellular vaccines were around 85 per cent efficacious in preventing typical whooping cough.
Last Reviewed: 04 February 2011