Closing schools for long periods could reduce the spread of swine flu, ease its burden on hospitals and potentially limit the number of deaths it causes, two leading experts argue today.

The fact that children are more infectious and more vulnerable to the H1N1 virus, resulting in it spreading among them at great speed, means that prolonged closure of schools is necessary, according to Dr Simon Cauchemez and Prof Neil Ferguson of Imperial College London.

The government may need to rethink its existing policy of schools staying open during the pandemic before the UK's 30,000 primary and secondary schools return from their summer holidays, if swine flu has become more severe by then, warn Cauchemez and Ferguson, who work in Imperial College's department of infectious disease epidemiology.

The two experts do not specify how long any closure should last but say that it may need to be "prolonged" in order to be effective, and recommend that "it would seem sensible for all countries to at least have plans for reactive closure".

Around 20 schools in Britain where pupils contracted swine flu were shut in May at the start of the pandemic in an effort to stop it spreading.

But that attempted containment was abandoned when the numbers of people affected rose rapidly. More than 60% of the cases of swine flu so far have been in young people aged 18 or younger, with incidence highest among five- to 15-year-olds.

Writing in the August issue of The Lancet Infectious Diseases, the authors say: "It is ... hoped that closure of schools during the pandemic might break the chains of transmission, with the following potential benefits: reducing the total number of cases; slowing the epidemic to give more time for vaccine production; and reducing the incidence of cases at the peak of the epidemic, limiting both the stress on healthcare systems and peak absenteeism in the general population, and thus increasing community cohesion".

Experience of school closures in other countries during previous flu epidemics in other countries shows that the tactic brings benefits, they say. In Israel in 2000, for example, teachers went on strike during a flu outbreak. When they did fewer people went to see their doctor or hospital emergency department and fewer patients were diagnosed with a respiratory tract infection or viral infections. But when the strike ended and schools opened again, infections resumed rising.

Similarly, a study of school holidays in France between 1984 and 2006 shows that school holidays prevent about one in six cases of flu and suggests that a policy of proactively closing schools as a preventative measure could cut the number of people getting infected by between 13% and 17% and by between 38% and 45% during the peak of the outbreak.

They also say that study of the 1918 flu outbreak in America and Australian cities indicate that shutting schools, in tandem with closing churches and improved hygiene, could have reduce the death toll by between 10% and 30%, and as much as 50% in some cities at the height of the outbreak.

However, the authors also point out that school closures have massive side effects. A 12-week closure would cost between one and six% of GDP, according to UK and American studies. And as many as 30% of the entire NHS workforce may need to be off to look after children. In addition, the question of how children who are off school should mix with each other is "a key uncertainty".

Headteacher leaders have been calling for teachers to be among the first to be vaccinated along with healthcare workers to prevent the forced widespread closure of schools due to lack of staff.