Some doctors here are vaccinating women above the age of 26 against cervical cancer although the guidelines state that the drugs should be given only to females aged nine to 26.

The doctors feel that the 26-year age limit is an arbitrarily set figure, and even if a woman is sexually active, she can still benefit from being vaccinated with either Cervarix or Gardasil.

'Many doctors, myself included, administer the vaccine to women older than 26 years of age,' said DrQuek Swee Chong, senior consultant and head of the preinvasive and screening unit of the department of gynaecological oncology at KK Women's and Children's Hospital.

'This would be considered 'off-label' use. It is not illegal to prescribe the vaccine in this manner as long as the women are aware of the potential benefits, limitations and risks, which should be explained to all women anyway,' he said.

He added: 'It is up to the drug companies, on the basis of good clinical research data, to apply to the relevant authorities for an extension of the age limits. This is not the remit of individual doctors.'

The oldest woman he has given the vaccine to is 47.

Cervarix and Gardasil are manufactured by drug firms GlaxoSmithKline (GSK) and Merck Sharp & Dohme respectively. Gardasil got the green light here in 2006 and Cervarix in 2007.

The two vaccines produce an artificial immunity to certain strains of high risk Human Papilloma Virus (HPV), mainly types 16 and 18, and can potentially prevent 70 per cent of cervical cancers.

A total of 15 high risk types have been identified. The virus is sexually transmitted.

HPV infection is extremely common, affecting between 50 per cent and 80 per cent of the female population at some stage in their lives, said DrQuek.

'Fortunately, most people will clear the virus without even knowing they had it in the first place.

However in a small proportion of women, the infection may persist, and over time may lead to changes in the cells which may become cancerous,' he said.

The vaccines are applied in three doses over six months. Each dosage costs about $150.

While doctors here say that the side effects are few, media reported last week that 1,500 females in Britain developed paralysis, convulsion, and sight problems after using Cervarix.

In Spain, two girls developed similar problems and the authorities there have suspended the use of Gardasil temporarily.

Gardasil's overall rate of anaphylaxis, a serious total body allergic reaction that can be fatal, is 2.6 per 100,000 doses administered, much higher than other vaccines for measles-rubella and hepatitis B.

These occurrences have sparked controversy over the risks and effectiveness of the vaccines over time, but the United States Food and Drug Administration and the Centres for Disease Control and Prevention still think that Gardasil is 'safe and effective'. Cervarix has not yet been approved in the US.

Asked whether the vaccines could be given to older women, the Health Sciences Authority (HSA), which is in charge of regulating health products here, said: 'HSA has not granted approval for the HPV vaccines to be used in patients aged above 26. The evidence of benefits for use in this group of patients has not been conclusively demonstrated.'

It added that the USFDA is currently adopting the same position.

Still, four out of six doctors whom The Sunday Times spoke to believe the vaccines are suitable for women above 26.

'Nothing special happens to a woman once she turns 26 that makes the vaccine ineffective or dangerous,' said Dr Quek. 'The main thing to understand is that any woman, regardless of age, is at risk of exposure to the HPV virus once she becomes sexually active.'

Dr Wong Seng Weng, consultant medical oncologist at The Cancer Centre in Paragon Medical Centre, agreed.

'After a woman becomes sexually active, she may not have picked up all the HPV viruses,' he said.

'Even if she gets infected, her body can get rid of it most of the time within two years. But there is a tendency to pick it up again as they are not immune to it. Hence, it makes sense to vaccinate so they won't pick it up in future.'

Cervical cancer is the sixth most common cancer affecting women in Singapore and one woman dies of cervical cancer every five days.

Less than 1 per cent - or about 6,600 of 1.8 million women between ages 10 and 25 here - have gone for the vaccination.

Dr Quek said it is most effective for adolescent girls based on the assumption that they are not sexually active yet and that their bodies are able to respond strongly to all sorts of vaccinations.

But studies by GSK on Cervarix in 2006 showed that women up to age 55 could still benefit as they mounted very good immune responses to HPV vaccination.

'The age-26 is just an arbitrary cut-off age the researchers used for studies on the effectiveness of the vaccines. It does not make sense to me that a 28-year-old who has not had sex cannot get vaccinated due to the age limitation, yet a 21-year-old who has had sex can,' said Dr Quek.

However, some doctors remain cautious.

Dr Khoo Kei Siong said he does not encourage women above 26 to be vaccinated.

'In my view, the results from the studies done on whether older women can be protected are not conclusive.

Not all major drug regulatory agencies around the world view the use of vaccines for women above 26 favourably,' said the senior consultant in medical oncology in Parkway Cancer Centre.

Women who are vaccinated are still advised to go for their regular pap smear screening, which detects abnormal cells in the cervix.

Additional reporting by Teo Wan Gek

This article was first published in The Straits Times.