Britain's first swine flu vaccine trials are taking place in Leicester, the Mercury can reveal today.

In all, there are 175 volunteers taking part in the tests at Leicester Royal Infirmary.

Scientists hope they will help provide a long-awaited breakthrough in the fight against the virus, with a vaccine being made available as early as this autumn.

The Health Protection Agency has announced that the number of deaths from the illness in England rose from 27 last week to 36. But there has been a dramatic drop in the number of worried people calling their GPs. Calls from city patients dropped from 792 to about 250 last week, and in the county they fell from more than 1,500 two weeks ago to 380.

However doctors still fear a fresh wave of infections when schools and universities re-open this autumn.

Vaccine tests began two weeks ago and blood samples are now being taken to detect how much immunity the drug gives.

Because the infection is new, hospital experts say patients will need two doses of the vaccine to build up immunity.

The trial is being led by Dr Iain Stephenson, consultant in infectious diseases at Leicester Royal Infirmary and clinical senior lecturer at the University of Leicester.

He said test results should be known at the start of September, before the first batches of the vaccine are due to be delivered to the Department of Health.

The vaccine's safety is not in question.

He said: "There is nothing experimental about this.

"It is produced in exactly the same way as the seasonal flu vaccine which has been around since the 1940s and used by millions of people. It is only the 'swine flu' part that is different.

"It is almost certain two doses of vaccine will be needed. Unlike seasonal flu, where people's bodies are partly primed to fight the virus, swine flu is a new infection none of us has met before.

"Because of this your body needs a priming dose and then a boosting dose.

"The lower the dose the more of the vaccine can be shared among the population.

"The trial will also help determine how far apart the injections need to be given."

The first people to get the jabs are likely to be children under-five, pregnant women and those under 50 with health problems.

Dr Stephenson said: "The virus might just disappear but most people expect there will be a larger wave in the autumn – probably as the schools start going back.

"Most people will be susceptible but fortunately, at the moment, it is a relatively mild infection.

"The flu virus changes all the time and adapts but at the moment there is no sign the swine flu virus is changing."

Gemma Clark, a 20-year-old administration officer, at the University Hospitals of Leicester NHS Trust, was one of the volunteers who responded to an advert on the trust's internal website. She said: "I don't really want to get swine flu and I thought I would be helping other people by taking part in the trial. I have never done anything like this before but I would be happy to do it again."

Gemma, who is being given £75 for travelling expenses, has had the first jab and is waiting to have a blood test.

She said: "The injection stung quite a bit, but only for about 30 seconds.

"After that my arm was a bit sore for a day or two but otherwise I have not had any side effects."