An Oxford biotech firm has run out of stock of yellow fever vaccine, triggering a nationwide shortage.

Chiron Vaccines, part of US-based Chiron Corporation, which has its UK headquarters at Oxford Science Park, was one of the two suppliers of yellow fever vaccinations until January 27, when it said the vaccine went "out of stock".

With Sanofi Pasteur the only company supplying the UK market, there is now a nationwide and increasingly worldwide shortage of the vaccine.

As reported in yesterday's Oxford Mail, John Kilgour, 29, of Howard Street, east Oxford, who is due to travel to Trinidad and Tobago, had to go to Reading to have a yellow fever immunisation. He could not find a private clinic in Oxford which had the vaccine.

Chiron, which is the fifth-largest vaccine business in the world, was at the centre of the US flu vaccine crisis last October, when its flu vaccine Fluvirin could not be exported to America after it was found to be contaminated.

Chiron, formerly Powderject, resumed production of Fluvirin at its factory in Speke, Liverpool, last month, but said it could not give any indication of when it would be able to supply the yellow fever vaccine.

Spokesman Rob Budge said: "We have told our customers we will get back to them as soon as we know we have stock. We're working hard on the situation. It's a complex production process. Different suppliers do go out of stock from time to time.

"It's not a situation we want to be in and we're apologising to our customers for that."

When asked when the firm would be able to produce the vaccine again, Mr Budge said he could not go into the technicalities of the production cycle.

He added: "There's not a huge number of yellow fever vaccines given in the UK, particularly if you compare it with childhood vaccines."

But the shortage is such that the Travel Health Network and Centre, a Department of Health-funded organisation, has advised health workers to carefully prioritise immunisations.

A message on its website states: "Until the shortage of vaccine is resolved, we suggest practices continue to prioritise the administration of vaccine by considering the risk of yellow fever at the destination and the immediacy of departure."