The vaccine works by making girls immune to strains of a virus
The Cervarix jab has been given to more than a million girls in the UK to protect them from the virus that causes cervical cancer, with many more set to follow.
What is it and how does it work?
Two vaccines have been developed - Gardasil and Cervarix.
Both target a sexually transmitted disease, human papillomavirus (HPV) which is thought to be behind 99% of cervical cancer cases.
The vaccines are most effective when administered to girls before they become sexually active - so before they potentially come into contact with HPV.
They are said to be 100% effective in protecting against certain strains of the virus - which frequently does not produce any noticeable symptoms.
In the UK, Cervarix is the vaccine of choice. It protects against the two strains of HPV (16 and 18) that cause cervical cancer in over 70% of women.
Was Cervarix a popular choice?
There was some controversy about its selection over Gardasil.
Some experts suggest Gardasil would have been a better option because it targets four strains of HPV - two responsible for cervical cancer (16 and 18) and two causing the less serious condition of genital warts (6 and 11).
Gardasil is used by the majority of vaccination programmes worldwide which are already up and running.
However, the Department of Health in England insists Cervarix came out on top after a rigorous assessment.
How does HPV cause cancer?
There are over 100 types of HPV but only 13 of them are known to cause cancer. The others are harmless or cause genital warts.
Most HPV infections clear up by themselves, but in some people the infection can last a long time.
HPV infects the cells of the surface of the cervix (the neck of the womb) where it can stay for many years without you knowing.
The HPV virus can damage these cells leading to changes in their appearance. Over time, these changes can develop into cervical cancer.
How has the vaccination programme rolled out?
Girls aged 12 and 13 started to receive the jab from September 2008 in England, Scotland and Wales.
A two-year "catch-up" campaign for girls up to the age of 18 is due for launch in autumn 2009.
The vaccine is given in three injections over six months.
It is likely to be done in schools but primary care trusts will be responsible for organising the programme in their area and could also ask girls to visit their GP.
How many lives will it save and when will we see the benefits?
Hundreds each year, potentially. The vaccine could prevent 70% of the 1,120 deaths that cervical cancer claims annually.
But it will take a while for this to manifest itself. Cervical cancer is thought of as a younger person's disease, but it often strikes women in middle age and later.
So it could be decades before the cervical cancer rates start to decline dramatically.
For this reason, the cervical smear test - a three-yearly examination - will continue.
How safe is the vaccine?
So far 1.4m doses of Cervarix have been given to people in the UK, and millions have received the jab around the world.
It underwent extensive safety checks before its introduction, and so far its safety record has been good.
A minority of people develop minor side-effects, such as sore arms, swelling at the site of injection and dizziness.
Adverse reactions to Cervarix and Gardasil
4,567 represents the total number of reactions reported in the UK between 14 April 2008-23 September 2009. In the US figures represent reactions between June 2006 and June 2009.
However, experts say a small number of severe allergic reactions are inevitable, and do not mean that the vaccine is not safe.
In the UK, the risk of severe, life-threatening reactions after immunisation has been estimated at about one per million vaccine doses.
It is not clear whether the latest death is a result of a reaction to the vaccine, or to an underlying health condition.
However, the batch from which that particular jab came has been removed, and tests are being carried out.
Medical experts have expressed concern that the latest death could put people off allowing their children to receive the vaccine unnecessarily.
In some cases people may have a psychological response, believing they have symptoms when in fact no physical reaction to the vaccine has occurred.
Gardasil has a similar safety record to Cervarix.
What should you do?
The Department of Health has said there is no reason to suspend the vaccination programme.
Anybody who is concerned is advised to speak to their GP about their concerns, visit the NHS Choices website at www.nhs.uk or call NHS Direct on 0845 46 47.
Do experts back mass vaccination?
They are pretty unanimously in favour, although all warn not to expect results overnight.
Several stress that while the financial investment may be huge, in the long term the money will be more than paid back by saving on treatment for those affected and phasing out smear tests.
"This is this first time a universal vaccine programme has been announced in the UK which is aimed specifically to prevent cancer," said Professor Adam Finn, expert in paediatrics at the University of Bristol Medical School.
"A lot of work now needs to be done quickly to provide information about the vaccines to be used to the girls who will receive them, their parents, their teachers and the doctors and nurses who will be involved in delivery."
Some Christian groups have expressed unease, concerned that the jab may encourage promiscuity.
Colin Hart, director of the Christian Institute, said the way to tackle the problem was not to offer injections, but to tell girls not to have under-age sex.
Are there implications for other cancers?
This immunisation is a huge step forward in the fight against combating the second most common cancer in younger women.
But cervical cancer is unique in the sense that it is in many cases sparked by HPV.
The jab does not vaccinate against cancer but against the virus, and so it would not provide protection against the many other forms of the disease.