A new study looking at young women in Australia who were vaccinated with Merck & Co’s Gardasil to prevent cervical cancer shows that they were five to 20 times more likely to suffer from anaphylaxis than girls in comparable school-based programmes, though the human papillomavirus jab is still “remarkably safe”, the authors conclude.

The study, published in the Canadian Medical Association Journal and carried out by Australian researchers, looked at 114,000 women. They found 12 suspected of anaphylaxis, and confirmed 8 of these, in a 2007 vaccination programme in New South Wales. Symptoms included difficulty in breathing, nausea and rashes.

Study author Julia Brotherton and colleagues said the reasons for an increased rate of anaphylaxis may include possible allergic reaction to the vaccine components or enhanced adverse event surveillance. It could also be the result of higher rates of anaphylaxis in women from mid-adolescence compared with men, and an apparent increase in incidence of anaphylaxis in Australia, but the researchers conclude that anaphylaxis following the HPV vaccine is rare and the programmes should continue.

The study comes at a time when the wisdom of widespread use of Gardasil and GlaxoSmithKline’s cervical cancer jab Cervarix, in terms of both safety and cost-effectiveness. Widescale HPV vaccination programmes are beginning in Europe and North America and Dr Brotherton stresses "the importance of good training for staff administering vaccines in school or other settings in the recognition and management of suspected anaphylaxis and its reporting."

Anaphylaxis is a rare but serious adverse event "and highlights the importance of vaccine safety studies after vaccine licensing and careful management of reactions in immunisation clinics", says Neal Halsey, Institute of Vaccine Safety, Johns Hopkins Bloomberg School of Public Health in a related commentary. He states that "before concluding that the HPV vaccine is associated with higher rates of anaphylaxis than other vaccines everywhere, cases in other populations should be reviewed.” He added that as of July 21 this year, 11 cases have been reported in the USA in 2008 and over 13 million doses of Gardasil had been distributed as of the end of 2007.

A CMAJ editorial states that this study indicates the HPV vaccine is "remarkably safe”. The study provides an excellent opportunity for Canada's public health community "to restart public discussions about the safety of the HPV vaccine, the precautions taken to mitigate risks if anaphylaxis occurs, and the care taken in surveillance for adverse events following vaccination," wrote Noni MacDonald, Matthew Stanbrook and Paul Hebert.