The following correction was printed in the Guardian's Corrections and clarifications column, Wednesday 22 July 2009

In the article below on swine flu we referred to a study by Simon Cauchemez, Neil Ferguson and others of whether school closures can mitigate such a pandemic. We said the study was published in the Lancet. Rather it was in the Lancet Infectious Diseases monthly journal.

Ministers were urged tonight to rethink their policy of keeping schools open through the swine flu pandemic after research showed that a shutdown would curb the spread of infection and limit the number of deaths.

As Andy Burnham, the health secretary, announced that a flu helpline to take the pressure off GPs' surgeries would go live this week, two infectious disease experts said school closures should be considered to reduce the number of cases and buy time until a vaccine is available.

Schools across Britain have now broken up for summer holidays, and experts hope this will help to slow the spread of the virus. But there are fears that when classes resume in the autumn the number of cases will increase rapidly.

School closures would cause serious difficulties for working parents, lead to a 1% loss in GDP through absenteeism and see as many as 30% of NHS staff having to take time off just when they are needed to treat growing numbers of patients.

In a study published in the Lancet , Government adviser Professor Neil Ferguson and Dr Simon Cauchemez, both of the department of infectious disease epidemiology, Imperial College London, said "prolonged" closures could reduce the scale of the outbreak by 13-17% and at the pandemic's peak shutting schools could bring down the number of cases by 38-45%.

"It is therefore 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-wide resilience," the researchers said.

Such a move would also raise the question of what should be done with millions of schoolchildren during a prolonged shutdown, they added. The authors said that governments in Europe and North America might have to take such a step after they studied the impact of school closures during flu epidemics in other countries stretching back to 1918.

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

About 100 schools closed after the start of the outbreak in May, but soon reopened when official advice changed because swine flu was becoming so prevalent.

Last night the schools department said it was sticking with the current guidance, which is not to close schools. Ed Balls, schools secretary, said: "Now that the virus is established in the community, expert advice is that there is no longer a strong case for closing schools to contain the spread of infection. We will be monitoring the situation closely over the school holidays and will review the evidence in late August."

The department's emergency planning group, Cerg, is now solely concerned with orchestrating schools' response to the spread of swine flu and updating ministers daily on the situation.

Professor Steve Field, chairman of the Royal College of General Practitioners, said ministers should keep open the possibility of school closures. "It's something that shouldn't be discounted if it's the height of the pandemic," he said. "It would depend on how the pandemic has developed. The Lancet study demonstrates that it would slow down the transmission of the virus and might cut down the number of people who get serious illness and who die."

Mick Brookes, general secretary of the National Association of Headteachers, called for a balanced view of the risks. "Even one person dying is a tragedy but if the mortality rate is the same of any other flu that needs to be kept in perspective," he said. "If more and more people become infected closures may well become inevitable. Younger children are more at risk so it might be right to close early years centres and nurseries first."

Martin Ward, deputy general secretary of the Association of School and College Leaders, said schools could set up internet-based classrooms if there were long-term school closures. "But with the best will in the world they are not going to make the progress they would have if they had been in school," he said.

Pregnant women may want to steer clear of crowded places in order to reduce their chances of catching the virus, the government's chief medical officer, Sir Liam Donaldson, said yesterday. The swine flu virus's current known level of risk meant that expectant mothers should not stop using public transport, going to work or attending events and family gatherings, he said. But he added: "Some mothers-to-be may wish to continue their day-to-day activities but exercise their choice now, on a highly precautionary basis, to avoid large densely populated gatherings where they have little control over personal contact."

He was trying to end the confusion over what steps pregnant women should take to avoid catching the virus after conflicting advice from medical organisations .