The Big Question: Is the cervical cancer vaccine safe, and should girls stop taking it?

Why are we asking now?

The sudden death of schoolgirl Natalie Morton, 14, after receiving the cervical cancer vaccine, Cervarix, at the Blue Coat Church of England School in Coventry has raised fears about the Government's national immunisation programme against the disease.

Parents of teenage girls due to receive the jab are questioning whether it is worth the risk and politicians are demanding ministers explain why they chose Cervarix over a rival vaccine.

Is the jab safe?

No drug is absolutely safe in the sense of being 100 per cent free of side effects. All drugs cause unwanted symptoms in some people. In the case of Cervarix, made by GlaxoSmith- Kline, the commonest side effects are pain, swelling and redness at the injection site which quickly wears off. But very rare catastrophic events cannot be ruled out. Natalie Morton's death may be one of these, but it may also have nothing to do with the vaccine – we won't know until the results of the post mortem are available.

Has it been tested?

Cervarix was extensively tested before it was introduced (it is now licensed in 95 countries) and its safety has been monitored closely since. Millions of doses have been given. David Elliman, a vaccine expert at Great Ormond Street Hospital, said: "We are not aware of any similar occurrence previously. Rarely a person does have a life-threatening allergic reaction after a vaccine, medicine or food. That is very rarely fatal after a vaccine."

Is there an alternative?

Yes. It is called Gardasil and is made by Merck. Like Cervarix, it protects against two of the principal strains of Human Papilloma Virus (HPV) that cause cervical cancer but in addition offers protection against two other strains that cause genital warts. This has made it the vaccine of choice in most countries around the world. The UK is the only leading country to have chosen Cervarix.

Why did the UK choose Cervarix?

Probably because it was cheaper. But we don't know because the Government has never published its full reasoning. Andrew Lansley, the Tory shadow health secretary, yesterday reiterated his demand that ministers should do so. GlaxoSmithKline have argued that their vaccine is "stronger and longer" than Gardasil – meaning that it delivers a stronger immune response which lasts for longer, so women are less likely to need a booster later in life. One of the unknowns about both vaccines is whether the protection they provide will be lifelong.

Haven't there been thousands of side effects?

Yes – associated with both vaccines. There have also been reports of deaths. This is part of the monitoring process. Doctors and the public are encouraged to report any adverse event that occurs around the time of vaccination, or could be linked with it, however unlikely the link might appear. Drug safety experts then scour these reports for patterns. Most of the reported side effects turn out to have no link – their occurrence at the time of vaccination is a coincidence. In the US, 30 deaths have been linked with Gardasil but the US Food and Drug Administration said in July 2008 that there was no pattern among them and where post mortems had been carried out they showed the deaths were explained by "other" factors.

What about serious adverse events in the UK?

Ashleigh Cave, 12, from Aintree, Merseyside, collapsed after receiving the Cervarix vaccine last December and was later admitted to hospital, apparently paralysed from the waist down, in a widely reported case. Guillain Barre syndrome was suspected, a rare condition which can cause paralysis and has been linked with other vaccinations. However doctors later dismissed this suggestion and said her illness was not linked to the vaccine.

Are there differences between the vaccines?

Yes. Cervarix contains an adjuvant, a chemical to enhance its efficacy and boost immune response; Gardasil doesn't. US authorities, which have not allowed any adjuvants in vaccines since the 1930s, refused Cervarix a licence in 2007 because of concerns that the adjuvant it contained, called AS04, resulted in "musculoskeletal and neuroinflammatory events". But in papers released earlier this month the Food and Drug Administration's advisory committee said additional research had shown no causal link with these events or with "spontaneous abortion" which Cervarix was also suspected of causing. It said other adverse events supposedly caused by the vaccine were "unremarkable". Analysts advised this could pave the way for Cervarix to be licensed in the US as a rival to Gardasil.

Why do we need a cervical cancer vaccine?

In England there are more than 2,000 cases of invasive cervical cancer each year and 900 deaths. The vaccine is expected to prevent 70 per cent of these. The mass immunisation programme began last year and 1.4 million doses have so far been delivered. The target is to vaccinate every girl aged 12 and 13 in England, Scotland and Wales and a catch-up programme for girls up to age 18 is to begin this autumn. The vaccine is given in three injections over six months and is organised by primary care trusts but delivered in schools.

Isn't it 99% effective?

Yes. But this is misleading. Cervical cancer is the first cancer shown to be caused by an infection, HPV. But there are scores of different strains of HPV, at least 15 of which cause cancer. Cervarix and Gardasil provide 99 per cent protection against the two commonest viral strains, HPV 16 and 18, which are together responsible for 70 per cent of cases of cervical cancer. So 99 per cent protection against the two commonest causes means about 70 per cent protection against cervical cancer.

Does it mean the end of cervical smear tests?

No. The vaccine has the potential to save hundreds of lives a year – but it will take decades for this to become apparent. Although cervical cancer is thought to be a young woman's disease – reinforced by reality TV star Jade Goody's death last March at the age of 27 – it also strikes women in middle and old age. In addition the vaccine does not provide complete 100 per cent protection. So the regular three yearly smear test will continue for many years yet.

Is there any opposition?

Yes – mainly from Christian groups who have argued the jab would increase promiscuity. The Family Education Trust says there is a danger the vaccine will give young girls a "false sense of security" leading them to think they are protected against the worst effects of promiscuity. It said the "best protection" was to avoid sex outside marriage.

What about immunisation?

As a precaution, the batch of Cervarix from which Natalie Morton was vaccinated has been quarantined, in case there was some problem with its manufacture. However, experts said no other significant problems had been reported with the batch and girls who had already received jabs from the same batch had no cause to worry. They urged that the immunisation programme should continue.

Is vaccination against cervical cancer wise?

Yes...

*The vaccine has been extensively tested and millions of doses have been delivered

*It is effective against two of the main viruses causing cervical cancer providing 70 per cent protection

*In decades to come, the vaccine is expected to save hundreds of lives each year

No...

*There is always a risk, with any vaccine, of an extremely rare but severe allergic reaction

*The vaccine is most effective in young girls who have not yet started sexual activity

*Regular cervical smear tests check for cancer which can be treated if caught early