Britons going on their summer holidays were warned today not to travel if they had swine flu.

The Department of Health, which is currently setting up a new pandemic flu service, advised people with the virus to delay journeys until symptoms had gone.

As the Government awaits the arrival of a vaccine for the H1N1 virus, the end of the school year coincides with an outbreak affecting thousands.

Officials warned that visitors to a number of countries would have to face strict screening procedures as the illness spreads.

This was demonstrated in China, where 52 British schoolchildren and teachers were placed in quarantine in a Beijing hotel after four teenagers from London were diagnosed with swine flu.

According to the DoH, holidaymakers should take medication such as paracetamol with them and avoid public places if they fall ill.

People travelling to Europe should carry a European Health Insurance Card (EHIC), the advice added.

If they catch swine flu - symptoms of which are a high temperature as well as two or more of a list including headache, sore throat, runny nose and aching muscles - while abroad, they should not travel home until recovered.

Health Secretary Andy Burnham, who is due to give a statement to the Commons tomorrow, said: "I want families to go on their holidays and have a great time this summer, and mums and dads shouldn't worry unnecessarily about swine flu.

"But, just as they would anyway, parents should keep a close eye on their children's health.

"If you're going abroad, as ever, make sure you know where you can get medical advice and if you're holidaying in the UK, remember that from the end of this week alongside GP services, you'll also able to phone the national pandemic flu service hotline for advice."

A spokesman for Abta, which represents travel agents and tour operators, said: "It's very sensible advice and we would agree with it."

He added that the cost of cancellation due to swine flu would be covered by travel insurance.

The advice came as a senior adviser to the Government moved to calm concerns over the swine flu vaccine after questions were raised about whether it will have been sufficiently tested before it is used.

The first deliveries of the vaccine are expected to arrive next month, sparking concerns that doses will be administered before full clinical trials are completed.

But Professor Sir Gordon Duff, co-chairman of the Scientific Advisory Group for Emergencies, said the "benefits far outweigh the risks".

He added: "These core vaccines have been tested on 5,000-6,000 people already, with no serious adverse effects.

"It is inconceivable that in the UK we would consider a vaccine without giving a full scientific appraisal of its benefits and theoretical risks. That is just what these risks are - theoretical."

The Tories called on the Government to confirm in the statement it should "proceed only with a licensed vaccine and also initiate a public debate about priorities for vaccination when it is available".

Thousands of people in Britain have been affected by swine flu and the total number of UK deaths linked to the virus stands at 29.

Three of the year nine (aged 13-14) children taken ill in China were from the Central Foundation Boys School in Clerkenwell, while one attended Parliament Hill School in Camden, organisers said.

The quarantined group was among a party of around 600 British students and teachers from across the UK who had travelled to China.

Organised by the Specialist Schools and Academies Trust, the British Council and Hanban, a Chinese organisation linked to Confucius Institutes, and part-funded by the Department for Children, Schools and Families, the two-week trip was intended to enable the teenagers to learn more about the country's culture and language.

A spokesman for the Specialist Schools and Academies Trust said the students were "making an excellent recovery and being looked after very well by hospital staff".

"We hope the students make a quick recovery and can join their peers on the rest of the visit as soon as possible," he added.

The FCO website states that medical screening for the swine flu virus has been introduced at several airports for passengers arriving on international flights, including in China.

In the section relating to travel advice for China, the guidance states: "The Chinese government continues to place great emphasis on screening and surveillance, rapid detection, quarantine and treatment."