Life span of anti-cancer jab queried
A leading international vaccine expert is questioning whether a new anti-cancer jab lasts long enough to protect girls from cervical cancer.
Dr Diane Harper said Gardasil, the new vaccine against human papillomavirus (HPV), had not been proven to last more than five years.
Young girls, vaccinated at 12, may therefore not be exposed to the virus until after the vaccine had waned, she said.
Harper, a principal investigator for clinical trials of Gardasil and Cervarix, is a professor and vice-chair of research at the University of Missouri-Kansas City School of Medicine in the US.
New Zealand health officials said they did not yet know if a booster would be required. However, Gardasil was low risk, was not a proven cause of any deaths and lasted at least five years if not longer.
Harper said if Gardasil lasted 15 years, vaccinating an 11-year-old would protect her until she was 26 and prevent some pre-cancers and postpone most cancers. If the vaccine lasted less than 15 years, then no cancers would be prevented, only postponed, she said.
"If Gardasil is given to 11-year-olds and the vaccine does not last at least 15 years there is no benefit, only risk."
Gardasil protects against four types of HPV including two linked to genital warts.
Harper said Gardasil maintained antibodies only against the HPV 16 type, associated with cervical cancer, for five years. The World Health Organisation said Gardasil has remained active for five years of ongoing observation.
Dr John Holmes, the Ministry of Health's chief adviser for population health, disagreed with Harper's claim that unless Gardasil lasted for 15 years it created more risk than benefit to young girls.
"Adverse effects are usually mild with a serious allergic reaction, like a peanut allergy, the only severe reaction," he said.
There were more cases of fainting and blood clots associated with Gardasil than other vaccines. "There is no evidence suggesting the vaccine is behind two reports of unusual neurological illness and the deaths of two young women being investigated by US medical authorities," he said.
Holmes said Gardasil provided proven immunity for at least five years with some clinical trials supporting an 8.5-year lifespan. Evidence suggested it would not require a booster, he said.
Holmes said the long development period of cervical cancer meant it was too soon to see any population benefits from immunisation. But vaccination would reduce cervical abnormalities and pre-cancers.
"There will be fewer abnormal smear test results which will free up health sector resources and see fewer women have to go through the stress of follow-up examinations and treatment."