#4328
In case anyone had any doubts beforehand, the pandemic of 2009 demonstrated that NPIs (non-pharmaceutical interventions) such as school closures, hand washing, and staying home when sick are our first line of defense during a disease outbreak.
Vaccines take months to manufacture, and would likely remain in short supply for months beyond that.
While novel H1N1 proved to be a moderate pandemic virus, with a low CFR (Case Fatality Ratio), the next global health challenge may prove far more daunting.
The good news is novel H1n1 afforded us an excellent opportunity to try various mitigation strategies around the world, and we can now begin to compare their relative efficacies.
School closures were already part of the US government’s NPI plans for a severe pandemic, and were instituted in the early days of the swine flu outbreak. But school closures have a cost in terms of social and economic impacts, and must be balanced against the benefits.
Although the assumption has been that school closures would reduce transmission of a pandemic virus, the question has always been: How much?
We now have a study, based on school closures in Hong Kong last summer, that give us at least a partial answer to that question.
Of course, the old saw that `If you’ve seen one pandemic, you’ve seen one pandemic’ still holds. Methods and rates of transmission can vary from one virus to another, and quite frankly, from one region or society to another.
That said, researchers in Hong Kong have come up with a number they feel illustrates the benefits of early and sustained school closures during this past summer.
Their work appears in this month’s CDC’s Journal of Emerging Infectious Diseases.
DOI: 10.3201/eid1603.091216
Wu JT, Cowling BJ, Lau EHY, Ip DKM, Ho L-M, Tsang T, et al. School closure and mitigation of pandemic (H1N1) 2009, Hong Kong. Emerg Infect Dis. 2010 Mar; [Epub ahead of print]
School Closure and Mitigation of Pandemic (H1N1) 2009, Hong Kong
In Hong Kong, kindergartens and primary schools were closed when local transmission of pandemic (H1N1) 2009 was identified. Secondary schools closed for summer vacation shortly afterwards. By fitting a model of reporting and transmission to case data, we estimated that transmission was reduced ≈25% when secondary schools closed
A 25% reduction in transmission is actually better than some previous studies had suggested, and as the authors point out below, the benefits of school closures probably extended into the greater community as well.
Furthermore, assuming that children are responsible for up to half of all community transmission (8), it is likely that protection of younger children had substantial indirect benefits. Previous studies have suggested that sustained school closures during a pandemic could reduce peak attack rates and prevent 13%–17% of total cases in France (8) or <20% of total cases in the United Kingdom (3).
Our finding that the reproductive number declined from 1.5 during the kindergarten and primary school closures to 1.1 during summer vacation suggests that a much more substantial drop in attack rates would result from sustained school closures.
This study, when combined with others that will no doubt arise from the pandemic, should give public health officials better data to base their school closing decisions on for the next pandemic.
It still remains a judgment call, of course. You still have to balance the severity of the illness against the impact of closing schools.
But at least now we are getting a better idea of what might be gained by such measures.
