SciDev.Net

A vaccine could prevent abnormal cells like these growing on the cervix

Ed Uthman, MD

Promising results in an ongoing global trial of a vaccine against cervical cancer have not yet convinced the Thai government to include the vaccine in the country's national healthcare programme. 

A team of international researchers revealed the interim results of a four-year trial in The Lancet last week (28 June).

The vaccine is designed to protect against human papillomavirus (HPV) types 16 and 18, which between them cause 70 per cent of cervical cancer cases worldwide.

A total of 9,258 women aged between 15 and 25 years received the vaccine, of which 1,852 were from Thailand. Some may already have been infected with HPV.

The study shows the vaccine is 90.4 per cent effective in preventing precancerous cervical lesions associated with HPV 16 and 18 over an average follow-up period of 15 months.

This means that the vaccine can prevent cells in the cervix infected with HPV types 16 and 18 from changing into cancerous cells, explains the Thai investigator of the group, Unnop Jaisamran, from the Reproductive Medicine Unit of Chulalongkorn University in Bangkok, Thailand.

But it doesn't necessarily offer protection against cancer for women infected with other cancer-causing types of HPV, he says.

The vaccine also boosts immunity, being 80 per cent effective at preventing persistent infections caused by HPV types 16 and 18, he says.

It also seems to prevent persistent infections by other HPV types — 45, 31, 33 and 52 — although their efficacy rate has not been confirmed, he says.

The capacity for cancer screening is poor in Thailand, so the new vaccine could be a promising treatment option against the cancer for Thai women, says Jaisamran.

According to Thailand's National Cancer Institute, around 6,000 Thai women develop cervical cancer each year. About half die from the disease, largely from a failure to detect the cancer early.

Thawat Suntrajarn, chief of Thailand's Disease Control Department, says that despite the research being encouraging, the vaccine will not be included in the country's national healthcare programme at the moment owing to the cost of the vaccine, which is currently around US$480 per vaccination.

He said this is in the light of the fact that the country has a number of more urgent diseases to deal with, including bird flu, for which Thailand need a vaccine to be in place very soon.

Suntrajarn said the department is trying to improve screening in villages, which includes development of self-screening kits for cervical cancer to overcome the traditional reticence about sexual matters that stops many Thai women from consulting a doctor.

"It's not like the cancer is not critical, but we have to consider many things and we think we can deal with it in other ways at present. In the future, we may review economic losses and gains again to help us decide what we should do about it," said Suntrajarn.

Reference: The Lancet 369, 2161 (2007)