# 6125
Although not without its critics, extended school closures have been promoted as one of a list of NPIs (non pharmaceutical interventions) that might be used to slow the spread of illness during a severe influenza pandemic.
The chart above, taken from the PNAS journal article entitled Public Health Interventions and Pandemic Intensity During the 1918 Influenza Pandemic, shows the excess mortality in two American cities. The tall spike represents Philadelphia, while the lower curve represents St. Louis.
Many researchers believe the startling difference in attack rates, and mortality, in these two cities can be explained by the way each city dealt with the outbreak.
In St. Louis, the Health Department closed public venues such as schools, theatres and churches very early in the outbreak, while Philadelphia did not.
During the spring of 2009, when novel H1N1 first began to spread, schools closures were recommended by the CDC, and by other public health entities around the world.
By early May it became apparent that the severity of this particular influenza virus was less than originally feared, and many public health agencies moderated their recommendations (see CDC No Longer Recommending School Closures For A/H1N1).
Some school districts, in the U.S., and elsewhere around the world, continued to close schools on a case-by-case basis well into the fall of 2009.
School closings are controversial and they do not come without some social and economic costs (see The Debate Over School Closures).
Critics point out that working parents rely on schools to watch their kids for much of the year during the day, and many low income families benefit from the school lunch program.
And of course, when schools are closed during a pandemic, some kids may congregate elsewhere and spread the virus anyway.
While decisions on whether to close schools during a pandemic might well be trumped by parental concerns, it is important for policymakers to get some idea of the benefits that proactive school closings would generate.
To that end we’ve seen a number of studies that came out of the most recent pandemic, and while the results have not all been in alignment, many have indicated substantial benefit from school closures.
In a report that appeared last year in the journal Eurosurveillance (see Eurosurveillance: New Research On Pandemic Influenza), we saw several studies that attempted to quantify the benefits of school closures:
- Three studies out of Japan found a beneficial effect during the 2009 pandemic by using antiviral drugs and/or school closure (of varying length and timing) to interrupt its transmission.
- Conversely, a fourth study suggested that early school closures could have adversely affected herd immunity in the school environment, with lower cumulative infection rates in schools that delayed closure.
Last May (see NIH: School Closings Effective In 2009 Pandemic) we saw a report indicating that school closings in Mexico reduced disease transmission by as much as 37%.
This from the NIH.
Tuesday, May 24, 2011
5 p.m. EDTMexican flu pandemic study supports social distancing
Fogarty research published in PLoS Medicine
Eighteen-day periods of mandatory school closures and other social distancing measures were associated with a 29 to 37 percent reduction in influenza transmission rates in Mexico during the 2009 pandemic. The research was carried out by scientists at the Fogarty International Center at the National Institutes of Health and published in PLoS Medicine.
I’ve posted on a number of other studies of the effects of school closures over the past few years, including:
Study: Pandemic Mitigation by Early School Closure
Study: Student Behavior During Pandemic School Closings
School Closures Revisited
All of which serves as prelude and introduction for a new study, just out in the Annals of Internal Medicine, that looks at the effects of school closures in Canada during the 2009 pandemic.
Effects of School Closure on Incidence of Pandemic Influenza in Alberta, Canada
David J.D. Earn, PhD; Daihai He, PhD; Mark B. Loeb, MD, MSc; Kevin Fonseca, PhD; Bonita E. Lee, MD, MSc; and Jonathan Dushoff, PhD
Abstract (excerpts)
Background: Control of pandemic influenza by social-distancing measures, such as school closures, is a controversial aspect of pandemic planning. However, investigations of the extent to which these measures actually affect the progression of a pandemic have been limited.
<SNIP>
Results: The ending and restarting of school terms had a major effect in attenuating the first wave and starting the second wave of pandemic influenza cases. Mathematical models suggested that school closure reduced transmission among school-age children by more than 50% and that this was a key factor in interrupting transmission. The models also indicated that seasonal changes in weather had a significant effect on the temporal pattern of the epidemic.
<SNIP>
Conclusion: Analysis of data from unrestricted virologic testing during an influenza pandemic provides compelling evidence that closing schools can have dramatic effects on transmission of pandemic influenza. School closure seems to be an effective strategy for slowing the spread of pandemic influenza in countries with social contact networks similar to those in Canada.
While the entire article is behind a pay wall, for more on this we can go to the press release from McMaster University.
School closures slow spread of pH1N1
Should be considered as a control measure during pandemic outbreaks
Hamilton, ON (Feb. 6, 2012) - Closing elementary and secondary schools can help slow the spread of infectious disease and should be considered as a control measure during pandemic outbreaks, according to a McMaster University led study.
Using high-quality data about the incidence of influenza infections in Alberta during the 2009 H1N1 flu pandemic, the researchers show that when schools closed for the summer, the transmission of infection from person to person was sharply reduced.
"Our study demonstrates that school-age children were important drivers of pH1N1 transmission in 2009," says David Earn, lead author of the study published in Annals of Internal Medicine. Earn is professor in the Department of Mathematics and Statistics and member of McMaster's Michael G. DeGroote Institute for Infectious Disease Research (IIDR).
Alberta was the only Canadian province to continue extensive virologic testing throughout the first wave and continuously to the middle of the second wave of the 2009 pandemic, allowing researchers to identify the causes of changes in incidence as the pandemic progressed.
"The data that we obtained were so good that our plots immediately revealed a huge drop in incidence when schools were closed for the summer," says Earn. "Using state-of-the-art modeling, we then demonstrated that transmission was reduced by at least 50 per cent."
Although the severity of any novel pandemic virus will no doubt figure into the equation (as will the social and economic costs of shuttering schools), today’s study adds considerable weight to the notion that school closures could be an effective intervention during the next influenza pandemic.
