* Post-mortem under way to determine cause of death
* Batch of vaccine involved quarantined
LONDON, Sept 29 (Reuters) - GlaxoSmithKline's (GSK.L) cervical cancer vaccine Cervarix probably did not cause the death of a British teenager shortly after she was given the drug, a health official said on Tuesday.
"I think it is unlikely that will be the case," said Dr Caron Grainger, joint director of public health in the area where the 14-year-old girl died, when asked about the possibility of any connection between the death and Cervarix.
News of the death came shortly before a possible decision by U.S. health regulators on whether to approve Cervarix for sale in the United States.
"I think once we get into the investigation ... we may discover there is another cause of her death," Grainger told the BBC.
"The message for parents at this moment in time and for young girls receiving this vaccine is that you should go ahead with the vaccination," said Grainger, who works for the National Health Service in the central English city of Coventry.
Police are treating the girl's death as "unexplained" and said a post-mortem was taking place on Tuesday.
The teenager, named by a police source as Natalie Morton, fell ill on Monday after being vaccinated at her school under a national immunisation programme against the sexually-transmitted human papilloma virus (HPV).
NO PLANS TO HALT PROGRAM
Britain's Department of Health said there were no plans to halt the programme under which more than 1.4 million doses of Cervarix have been administered. "The vaccine has a strong safety record so precautionary measures are focused on the batch," it said in a statement.
Grainger said only about 2,000 people had suffered any adverse reactions to the immunisation programme and that these were mostly minor. GlaxoSmithKline said on Monday it was working with regulators to understand the case better.
Sudden teenage deaths, in general, are not unknown. "Unfortunately, some young people do die suddenly for a variety of reasons, including cardiac causes. Sometimes they have been entirely well before their death," said Dr David Elliman of London's Great Ormond Street Hospital for Children.
A small number of other girls at the Blue Coat Church of England School reported suffering from dizziness and nausea but were not admitted to hospital, health officials said.
The drug is given in three shots over six months.
The programme to vaccinate girls aged 12 to 13 began in September 2008. Cervical cancer is the 12th most common women's cancer in Britain, killing more than 1,000 women each year.
Should Cervarix gain U.S. approval it would compete with Merck & Co's (MRK.N) Gardasil, which has been on the U.S. market since 2006 and had sales of $268 million in the second quarter.
GlaxoSmithKline won support for its cervical cancer vaccine from an advisory panel to Japan's Health Ministry on Tuesday, putting it on track to be the first company to offer such a vaccine in the world's second-biggest drug market. [ID:nT327756]
GlaxoSmithKline shares were trading 0.4 percent lower in London at 1223 GMT, down slightly more than the broader market. (Editing by David Stamp)