Perhaps it was the jet lag. Or the attractive mother in the television ad, kissing the top of her child’s head as I sat watching in an American hotel room, thousands of miles away from my own daughter.

Apart from an appeal for an abandoned donkey sanctuary that I happened to catch when I was feeling a little hormonal, no advertisement had ever acted quite so effectively on my conscience.

“I chose to get my daughter vaccinated because I wanted her to be one less woman affected by cervical cancer,” the woman said gravely, before giving a little hug to her suspiciously cheerful teenager.

The ad was for a revolutionary human papilloma virus (HPV) vaccine, manufactured by the American pharmaceutical giant Merck, and ended with the message: “You have the power to choose. Ask your daughter’s doctor about Gardasil.” So I dutifully did my research and discovered that as the jab wasn’t yet available on the NHS, the vaccination would have to be done privately at a cost of £250.

Small price to pay, I figured, if my daughter Ellie was to become “one less” girl who had to worry about the second biggest cancer killer of women.

Ellie, then aged 14, simply shrugged when I told her she was going to have a jab that would protect her against cervical cancer. There was no soul-searching conversation; no demand to know why I wanted her to be vaccinated at such a young age against a sexually transmitted virus. In any case, I was pretty sure she knew about HPV.

Courtesy of teen mags and sex education lessons at school, Ellie and her friends are pretty much up to speed on all the perils of underage sex. (Children know far more than we think they do: at seven, Ellie once asked if I knew what being gay meant. When I attempted a fumbling Janet-and-Janet-style explanation of homosexuality, she snapped, “I know what it is – I just wanted to know if you did.”) So Ellie readily agreed to be given Gardasil in a series of three injections over the space of six months, and suffered no adverse reactions. She was, if you like, a pioneer. This September, every schoolgirl aged 12, 13, 17 and 18 – there are around 650,000 of them – will be given a letter inviting her to take part in the most expensive mass vaccination programme ever undertaken by a British government. (At a later date, the jab will also be offered to all girls aged 14-16 as well.)

The HPV vaccine was licensed for use in Britain more than a year ago, and last month it was announced the lucrative government contract had been awarded to Merck’s main rival Glaxo Smith Kline (GSK), which makes a vaccine called Cervarix.

Some time between the licence being granted and GSK getting the contract, I started investigating the story behind the vaccine for Channel 4’s Dispatches. Even before Britain had taken the decision to buy it, I discovered parents were starting to clamour for it – as one Glasgow GP confirmed. “It came with a great degree of hype about it,” she said dryly.

I soon started to wonder whether I had done the right thing by my daughter. Had my judgment been swayed by clever mar-keting? Had I inadvertently become caught up in “AstroTurfing” – the term used when companies are accused of creating a fake grassroots demand for a new product?

I also discovered that the path to herd immunity may not be as simple as the government is hoping it will be. Many parents were uncomfortable about the speed with which the vaccine had been introduced to this country. In Manchester, where Cervarix had been trialled for the past year, only seven out of 10 had agreed to their daughters taking part.

The reasons for this were varied. First and foremost, though, many were understandably reticent to sign up for the jab until they had a cast-iron guarantee that it was safe. The controversy over the MMR vaccine has put paid to the days when parents unquestioningly followed public health advice.

However, Margaret Stanley, a leading cervical cancer expert based at Cambridge University, assured me that unlike MMR the HPV vaccine is not live and is therefore biologically safe. However, it stops only two strains of HPV – so her main concern is that girls who are vaccinated should be given the strong message that they must still go to the doctor’s for smear tests from the age of 25.

Safety issues aside, some parents – particularly those from faith communities – are uncomfortable with what they see as the moral issues surrounding the vaccine. Two Catholic schools had opted out of the Manchester trial – chiefly because many parents felt that 12-year-olds were far too young to be told about a sexually transmitted virus. Indeed, some people believe that the vaccination programme may actually encourage promiscuity.

Dr Majid Katme of the Islamic Medical Association said: “My humble message to my Muslim community? Stick to your own religious moral code – you don’t need the vaccine. There are a lot of young girls who’ll say, ‘Oh, we’re protected, I have vaccine, I can go now and pick up these boys and sleep around’.”

I felt my hackles rising. If we were all told we could suddenly murder with impunity, I told him, that wouldn’t make us want to kill someone, would it? Equally, girls who refrain from having sex don’t do so because they fear they’ll get cervical cancer. They do so because they have high self-esteem and a strict moral code. The vaccine doesn’t change that.

However, the age of 12 does seem especially young. The idea, I was told, was to target every girl before she becomes sexually active; and, like it or not, there are some already having intercourse by then.

Another contentious issue is whether, at a cost well in excess of £100m a year, the vaccine is the best use of public money – or whether the money might save more lives if spent elsewhere.

Dr Angela Raffle, a public health consultant, explained the figures this way: “Take a million population: 14 women a year will die from cervix cancer. In that same population, 200 will die of lung cancer and 1,500 will die of heart disease. Cervarix is an expensive vaccine that, at very best, will make a small extra inroad into a disease that is already very uncommon. It’s probably not the best use of NHS resources.”

But David Salisbury, head of the vaccine programme for the Department of Health, is convinced that the vaccine is efficacious and worth the cost. “In an ordinary year of vaccination we would expect to save 400 lives,” he said. “Now multiply that up over 10 years, and that’s at least 4,000 lives [saved]. These are big numbers.”

Big numbers indeed, with a likely bill to taxpayers of close to £500m over the next few years.

Understandably, the competition to secure the government contract was fierce. So why did it choose to go for Cervarix? Merck’s Gardasil is the market leader and protects against four main types of HPV and 90% of genital warts. So it struck me as a curious decision to give the British contract to GSK’s Cervarix, which protects against just two nasty types of HPV – strains 16 and 18.

Earlier this month the British Medical Journal online published a paper that claims the government stands to make savings of £18.6m a year by choosing Cervarix over Gardasil. This has prompted a US public health expert to say that the health department decision implies it was willing to forgo health benefits to save money for other health projects.

Prior to licensing, both Merck and GSK ran powerful campaigns in the UK. Raffle told me that letters from both companies “started to come in thick and fast to primary care trusts, infectious disease specialists, individual practices, nurses, managers, everybody”.

She added: “This is a tried and tested technique that’s used a lot. The pharmaceutical industry creates the impression that there’s massive grassroots pressure for something – which works very well in a democracy because ministers respond to grassroots pressure. They don’t see it as self-interested lobbying by someone who has got a vested interest – the technical term for which is AstroTurfing.”

When I put this to Dr Pim Kon of GSK, she told me: “I certainly wouldn’t call it an AstroTurf or fake campaign. It is important that when you have innovative breakthroughs, such as vaccines that prevent cancer, that people are aware of them.”

On reflection my decision to vaccinate Ellie was undoubtedly swayed by a clever US television ad and by the “wonder drug” stories I’d read in the British media. So now that I know a little more about the vaccine would I still go ahead with that decision? Absolutely. And I’ll sign my four-year-old up for the free jab when she’s 12 too.

The clincher for me was meeting 22-year-old Claire Walker from Washing-ton in Tyne and Wear, who was diagnosed with advanced cervical cancer a year ago and was recently told that her condition is terminal. She has a two-year-old son, Alex.

As well as being in great pain, she’s had to come to terms with the fact that her life would have been saved if the vaccine had been available when she was 12. Her mother Lynn has this advice for other parents: “I wouldn’t hesitate. Even if it just saves one girl from going through what Claire is going through, then it’s worth it, isn’t it?” To my mind, it’s hard to argue with that.

Dispatches: The Jab That Can Stop Cancer is on Channel 4 at 8pm tomorrow

THE FACTS ABOUT THE HPV VACCINE

- Cervarix has been tested for 6½ years on more than 40,000 women. No deaths have been reported. The most common side effects are headaches, muscle pain, tiredness and swelling at the site of injection.

- The HPV virus is passed through sexual contact, but rarely causes serious illness in boys, so only girls are being offered the vaccine.

- The list price of the HPV vaccine is about £250 for a three-shot course. Although the NHS will pay less, it still costs about eight times as much as the hepatitis A vaccine, 13 times as much as the meningitis C vaccine and 40 times as much as the MMR.

- A survey of 2,000 teenagers found that one in five 14-year-old girls had had sex – with an average of three partners. Almost two-thirds of those had had unprotected sex and more than half had had a one-night stand.

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