British and French researchers reported that one in seven cases of pandemic flu might be averted if schools are closed and parents ensure that dismissed children don't simply congregate elsewhere, such as in formal or informal daycares or at the mall.
Their projections, generated by mathematical models, were published Thursday in the journal Nature.
Earlier modelling studies have predicted closing schools could dramatically lower the number of cases in a pandemic. This new work suggests those studies may have been overly optimistic.
"I think our predicted impact is quite limited, but not so limited that school closures should not be considered as an option," said senior author Neil Ferguson of the department of infectious diseases epidemiology of London's Imperial College.
"I mean, we're in the regime of 'It may be worthwhile, but the costs need to be borne in mind."'
Those costs are not trivial.
Children who are not in school need to be cared for. If parents need to stay home, that knocks healthy people out of an already weakened workforce. And not all parents can afford to stay home from work. Likewise, in some places children who don't have access to a school meal program will go hungry if other arrangements are not made.
Still, closing schools is one of the so-called non-pharmaceutical interventions or social distancing measures that pandemic planners have firmly in mind as they search for ways to blunt the blow of the next pandemic.
A key goal of this type of planning is to find ways to slow spread of disease so that health-care systems don't get swamped by a tidal wave of sick patients. Planners talk of "flattening the peak" - essentially spreading out cases so that hospitals can continue to function and more people remain healthy until vaccine becomes available several months into the pandemic.
Ferguson said his group's work suggests school closings could help achieve this goal.
"The one thing it might do by slowing down the epidemic somewhat - smearing it out - is reduce peak demand on health-care systems quite substantially."
The notion is based on the fact that children play a key role in the spread of seasonal flu. Whether that will be true in a flu pandemic remains to be seen.
In trying to estimate what kind of impact closing schools might have, Ferguson and his co-authors drew on data from France, where for more than 20 years a group of nearly 1,200 doctors have submitted daily reports on new cases of a variety of diseases, including influenza-like illnesses.
Using those data, the group was able to study what happened to rates of new infections when French schools break up for holidays and to use that as a basis on which to estimate what might happen in a pandemic.
The calculations suggest infection rates in children would drop by between 20 and 25 per cent, Ferguson said. But the modelling suggests the patterns of interactions of adults wouldn't change that much and the overall reduction in cases might be more in the order of 15 per cent.
That would mean that instead of an estimated 34 per cent of the population falling ill during a pandemic, only 28 per cent would be expected to get sick.
But all these figures are estimates, calculated using assumptions set by the modellers themselves. And not everyone is convinced academic projections will have much bearing on reality when a pandemic hits.
"I find these models to be of little help because I don't believe they're practical in the real world," said Dr. Michael Osterholm, an infectious diseases expert at the University of Minnesota who worked for years as that state's chief epidemiologist.
"For example, I am convinced we will not even have a chance to shut down schools before they are shut down on their own. Parents will not send their kids to school ... long before the actual transmission begins."
Osterholm pointed to school closings in the U.S. last fall, sparked by anxiety over the death of a Virginia high-school student. The 17-year-old died from an infection with antibiotic-resistant Staph, or MRSA.
A spokesperson for the World Health Organization said the Geneva-based agency is looking at these questions as its scientists draft the next version of its pandemic preparedness guidelines for member countries.
But Dr. Nima Asgari-Jirhandeh, a medical officer with the WHO's Global Influenza Program, said conditions vary so much from country to country that it will be difficult to come up with a single piece of advice on something like whether to close schools.
"If you've got a country where you've got 90 per cent of children going to school and when they come home they're going to come and play in front of the computer, that's a very different epidemiology of the disease than in a country where you've got 20 per cent of children going to school and when they leave they go and either play together or go and work," Asgari-Jirhandeh said.
"So you have to balance that. If I'm going close the school, is it actually going to work? It's not going to be so black and white."
