Study: The Effects Of School Closures During A Pandemic

 

 

 

# 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. EDT

Mexican 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.

 

(Continue . . .)

 

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."

(Continue . . . )

 

 

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.

»» Read More

NIH: School Closings Effective In 2009 Pandemic

 

 

 

# 5573

 

One of the most contentious issues during the opening days and weeks of the 2009 novel H1N1 outbreak was the wisdom of closing schools to reduce transmission of the virus.

 

Since the virulence of the virus was largely unknown during those opening weeks, school closures were recommended by the CDC, and by other public health entities around the world.  

 

The closing of schools, and other venues where people gather (sporting events, restaurants, shopping malls), has long been argued as being potentially an important mitigation strategy during a pandemic.

 

By early May (2009), however, it was 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.

 

In a future, more severe pandemic, the extended closing of schools will once again likely be considered to help reduce the spread of the virus.

 

It isn’t an easy decision, however.  School closings are controversial, and the issues are complex  (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.

 

 

It is important, therefore, to get some idea of the benefits that school closings would generate. To that end we’ve seen several studies over the past two years that have produced varying estimates.

 

Study: Pandemic Mitigation by Early School Closure

Study: Student Behavior During Pandemic School Closings

School Closures Revisited

Study: Effect Of School Closures On Viral Transmission

Today we’ve a new study by the NIH’s Fogarty International Center, Arizona State University and colleagues at the Mexican Institute for Social Security that appears in PLoS Medicine that looks at the epidemiology of the H1N1 outbreak in Mexico, and the effects of school closings and social distancing on its transmission.

 

Our first stop are a few excerpts (slightly reformatted) from NIH press release, which summarizes this research article nicely.

 

 

Embargoed for Release
Tuesday, May 24, 2011
5 p.m. EDT

Mexican 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.

 

The social distancing measures implemented by the Mexican health authorities in spring 2009 were effective in reducing disease transmission by more than one-third, the study found.

 

Social distancing interventions can be implemented during unusual infectious diseases outbreaks and include school closing, closure of movie theaters and restaurants, and the cancellation of large public gatherings. Mexico implemented a nationwide mandatory school closure policy during an 18-day period in late April and early May 2011.

 

The United States implemented school closure interventions on a local basis during the 2009 pandemic, but the impact of these interventions has yet to be evaluated.

(Continue . . .)

 

 

During a particularly severe pandemic, it has been suggested that schools could be closed for up to 12 weeks. While drastic, that strategy is based – in part – on some of the experiences from the last great pandemic in 1918.

 

 

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.

 

While are societal costs to closing schools and other public venues, studies continue to show that during a severe pandemic it might very well be worth doing. 

 

Here are some excerpts from the open access article in Plos Medicine.  Follow the link to read it in its entirety.

 

 

 

Characterizing the Epidemiology of the 2009 Influenza A/H1N1 Pandemic in Mexico

Gerardo Chowell, Santiago Echevarría-Zuno Cécile Viboud, Lone Simonsen, James Tamerius, Mark A. Miller, Víctor H. Borja-Aburto

Abstract  (Excerpts)

Background

Mexico's local and national authorities initiated an intense public health response during the early stages of the 2009 A/H1N1 pandemic. In this study we analyzed the epidemiological patterns of the pandemic during April–December 2009 in Mexico and evaluated the impact of nonmedical interventions, school cycles, and demographic factors on influenza transmission.

 

Methods and Findings

. . .   We estimate that the 18-day period of mandatory school closures and other social distancing measures implemented in the greater Mexico City area was associated with a 29%–37% reduction in influenza transmission in spring 2009. In addition, an increase in R was observed in late May and early June in the southeast states, after mandatory school suspension resumed and before summer vacation started. State-specific fall pandemic waves began 2–5 weeks after school reopened for the fall term, coinciding with an age shift in influenza cases.

Conclusions

We documented three spatially heterogeneous waves of the 2009 A/H1N1 pandemic virus in Mexico, which were characterized by a relatively young age distribution of cases. Our study highlights the importance of school cycles on the transmission dynamics of this pandemic influenza strain and suggests that school closure and other mitigation measures could be useful to mitigate future influenza pandemics.

»» Read More

Study: Pandemic Mitigation by Early School Closure

 

 

# 4758

 

 

One of the first steps taken by many countries to reduce the spread of novel H1N1 last year was the closing of schools in affected communities.

 

By early May (2009) it was 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).

 

But a future, more severe pandemic, the extended closing of schools will once again likely be considered to help reduce the spread of the virus.

 

It isn’t an easy decision, however.  School closings are controversial, and the issues complex  (see The Debate Over School Closures).

 

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.

 

Many parents, however, would take exception to the notion of sending their kids to school during a pandemic.  Not only would it, in their estimation - endanger their children – it increases the odds of them bringing the virus home to the rest of the family as well.

 

So it is important to get some approximation of the benefits that school closings would generate.  To that end we’ve seen several studies over the past year that have produced varying estimates.

 

Study: Student Behavior During Pandemic School Closings

School Closures Revisited

Study: Effect Of School Closures On Viral Transmission

 

Today we’ve another study appearing in BMC Infectious Diseases, this time from the School of Computer Science and Software Engineering at the the University of Western Australia.

 

Here is the abstract (slightly reformatted for readability).

 

Developing guidelines for school closure interventions to be used during a future influenza pandemic

Nilimesh Halder , Joel K Kelso  and George J Milne

BMC Infectious Diseases 2010, 10:221doi:10.1186/1471-2334-10-221

Published: 27 July 2010

Abstract (provisional)

Background

The A/H1N1 2009 influenza pandemic revealed that operational issues of school closure interventions, such as when school closure should be initiated (activation trigger), how long schools should be closed (duration) and what type of school closure should be adopted, varied greatly between and within countries. Computer simulation can be used to examine school closure intervention strategies in order to inform public health authorities as they refine school closure guidelines in the light of experience with A/H1N1 2009 pandemic.

Methods

An individual-based simulation model was used to investigate the effectiveness of school closure interventions for influenza pandemics with R0 of 1.5, 2.0 and 2.5. The effectiveness of individual school closure and simultaneous school closure were analyzed for 2, 4 and 8 weeks closure duration with a daily diagnosed case based intervention activation trigger scheme. The effectiveness of combining antiviral drugs with school closure was also investigated.

Results

Attack rate was reduced from 33% to 19% (14% reduction in overall attack rate) by 8 weeks school closure activating at 30 daily diagnosed cases in a community for an influenza pandemic with R0 = 1.5; whereas combined with antivirals, 19% (from 33% to 14%) reduction in attack rate was obtained.

 

For R0 >= 2.0, school closure would be less effective. An 8 weeks school closure strategy gives 9% (from 50% to 41%) and 4% (from 59% to 55%) reduction in attack rate for R0 = 2.0 and 2.5 respectively; however, school closure plus antivirals would give a significant reduction (~15%) in over all attack rate. The results also suggest that an individual school closure strategy would be more effective than simultaneous school closure.

Conclusions

Our results indicate that the particular school closure strategy to be adopted depends both on the disease severity, which will determine the duration of school closure deemed acceptable, and its transmissibility.

 

For epidemics with a low transmissibility (R0 < 2.0) and/or mild severity, individual school closures should begin once a daily community case count is exceeded. For a severe, highly transmissible epidemic (R0 >= 2.0), long duration school closure should begin as soon as possible and be combined with other interventions.

 

 

George E. P. Box, Professor Emeritus of Statistics at the University of Wisconsin, is often credited with coining the familiar adage:

 

“All models are wrong, but some models are useful.”

 

While imperfect, we use computer models every day to try to mathematically simulate real-life events;  everything from highway traffic flow to weather forecasting.

 

The authors describe some of the limitations to their study, including:

 

As the model is based on a population in a developed country the outcomes may not be applicable to populations in a developing country, where populations may be less mobile and have higher population densities.

 

We have focused on the reduction in the number of daily symptomatic cases and the cumulative illness attack rate as they are used for determining intervention effectiveness rather than focusing on influenza-related adverse events such as hospitalizations and deaths.

 

We also do not take account of possible antiviral drug resistance [40] [41] that may arise due to the implementation of antiviral drug strategies, as our main goal is to suggest refinements to policy guidelines for school closure.

  

In this case, the authors based their modeling on a medium sized (pop. 30,000) town in Western Australia. 

 

They find a substantial reduction in the spread of a future pandemic influenza can be achieved by the (extended) closing of schools at the optimum point in the local spread of the virus.

 

Gauging when and how long to close schools, however, may require information that isn’t always immediately available.  Such as the R0 (basic reproductive number) of the virus, the CFR (Case Fatality Ratio) or, the number of people actually infected in a community. 

 

Despite the fact that life is messy, and computer models aren’t perfect at depicting it, the entire report is worth reading.

 

This is how the authors sum up their study.

Conclusions 

Our simulation results give guidance as to public health policy decisions in the refinement of school closure strategies to be used in a future influenza pandemic. We have systematically evaluated school closure operational issues to determine when schools should be closed and re-opened to achieve the maximum reduction in influenza spread.

 

We found that the optimal timing of school closure depends both on the duration of school closure (which we assume will depend on the severity of the influenza strain, with strains that are more severe in terms of serious infection outcomes making longer periods of school closure acceptable) and on the transmissibility of the influenza strain (which influences the rate of growth and spread of the epidemic).

 

Accurate early estimates of epidemic characteristics such as the basic reproduction number and disease severity are thus necessary to achieve the maximum case reduction from school closure.

 

We found that a policy of allowing schools to close individually was much less sensitive to the precise timing of the intervention than a policy of simultaneous community-wide school closure, a valuable observation given the difficulty in determining the true degree of epidemic spread in the early stages of an outbreak.

»» Read More

School Closures Revisited

 

 

 

#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.

»» Read More

Japan: Nearly 14,000 Schools Closed Due To Flu

 

# 3901

 

In Japan, concerns over the Shingata Influ  (New strain influenza) run higher than here in the United States.  They are much quicker to don masks, close schools, and to take other steps to slow the spread of the virus.

 

At the start of October, only a little over 3,000 schools were closed in Japan.  That number has quadrupled to nearly 14,000  this week.

 

By contrast, in the United States -  with 2.5 times the population - only about 600 schools have closed this fall.

 

US school closures are rapidly approaching the level seen last spring, when 700 schools were closed during the initial outbreaks of the H1N1 virus.

 

A hat tip to Pathfinder on FluTrackers for this link.

 

 

Nearly 14,000 schools closed due to influenza

Thursday 29th October, 08:36 AM JST

TOKYO —

The health ministry said Wednesday that 13,964 educational facilities, including schools and kindergartens, canceled some or all of their classes due to influenza infections in the week from Oct. 18 to 24, up sharply from 8,534 reported a week earlier. Most of the facilities were hit by the new influenza, according to the Health, Labor and Welfare Ministry.

 

In the week through Sunday, 380 group infections involving more than 10 people have been reported on a preliminary basis, with Hokkaido leading other prefectures with 77 cases, followed by 58 in Tokyo, 36 in Osaka and 33 in Aichi.

»» Read More