Is school closure effective in reducing the impact of flu pandemics
The decision to close schools for prolonged periods should carefully consider the severity of the pandemic, according to a paper by MRC scientists in the August edition of The Lancet Infectious Diseases.
The review by Dr Simon Cauchemez and Professor Neil Ferguson from the MRC Centre for Outbreak Analysis and Modelling at Imperial College and colleagues examines the health, social and economic impact of closing schools during flu pandemics. Evidence from previous epidemics and pandemics from around the world has shown that early and prolonged school closure can substantially ease the burden on saturated hospitals by reducing the number of cases at the peak of the pandemic.
However, the intervention is unlikely to have a major impact on the total number of cases, is associated with high social and economical costs, and can potentially disrupt health care systems and other key services.
With more than 60 per cent of cases aged 18 or younger in the current H1N1 flu pandemic, children appear to be important vectors of transmission, and are more infectious and susceptible to most flu strains than are adults. These may constitute strong arguments for school closure in the current H1N1 flu pandemic.
The authors say: “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 health-care systems and peak absenteeism in the general population, and thus increasing community- wide resilience.”
However, school closures can also have negative effects on key workers, since, for example, many doctors and nurses are also parents—and may therefore need to be absent from work to look after children during an extended school closure. But since schools could need to close anyway due to teachers being sick, the authors say ‘it would seem sensible for all countries to at least have plans for reactive closure’.
Various flu outbreaks from the past are analysed in the paper. A teacher strike in Israel during a flu outbreak during 2000 saw reductions in doctor/emergency department visits and reductions in weekly numbers of respiratory tract infection diagnoses and of viral infections. However, once the strike ended (still during the outbreak), schools reopened and infections increased again. A study of school holidays in France (1984- 2006) shows that school holidays prevent one in six seasonal influenza cases, or, put another way, 16-18 per cent more people would be infected each year if schools had no holidays and were open all year. This French study suggests proactively closing schools could reduce flu cases by 13-17 per cent overall, and by larger proportions (38-45 per cent) during the peak of the outbreak. Finally, studies of the 1918 pandemic in US and Australian cities suggest that school closure (in combination with other measures including church closures, better hygiene) could have reduced mortality 10-30 per cent, with larger reductions in peak mortality (as high as 50 per cent in some cities). However, the strategy did not appear to have any substantial impact on spread when it was implemented during the 1957 pandemic in France or during a seasonal outbreak in Hong Kong.
Of course, infection control is only one side of the picture in school closures. UK and US studies put the estimated cost of a 12 week closure at between 1 per cent and 6 per cent of GDP. The impact of school closures would also be most keenly felt in poorer socioeconomic groups—for example, disruption of social programmes such as free meals that take place at schools.
The effects on the health-care system could also be serious and prolonged. In the UK, 30 per cent of the health and social care workforce is likely to be the main carer for dependent children (compared with an average of 16 per cent across all sectors). Thus there could be massive levels of absenteeism from work from the health workforce during a pandemic to look after children, in addition to absences caused by illness in healthcare workers. A survey of the UK Department of Health found that 77 per cent of respondents were women (78 per cent of UK doctors and nurses are female). Of these, 50 per cent had a dependent child aged under 16 years and 21 per cent said they would be likely to absent from work if schools closed. Peak absence from the healthcare workforce during a pandemic has been estimated as 45 per cent by Sadique and colleagues (30 per cent due to school closure, 10 per cent due to sickness, 5 per cent other).
Closing schools raises many operational issues, not insuperable but requiring careful local planning and school closures will not be possible in all countries and settings even if they might be desirable from a strictly health care perspective. Modelling suggests that if schools close before 1 per cent of the population becomes sick, the effect of closure remains close to maximum. The authors add that studies are needed into outbreaks at schools before, during, and after closure, along with the social and economic impact of the closure on households. The effect of closure on transmission in the wider community must also be assessed.
The authors say that the decision to close should also be based on the severity of the pandemic. They conclude: “The H1N1 pandemic could become more severe, and so the current cautious approach of not necessarily recommending school closure in Europe and North America might need reappraisal in the autumn. Another important uncertainty for pandemic planning is that individuals are likely to change their behaviours during a pandemic in a way that is difficult to predict. There is, for example, evidence that people reduced their contacts during the pandemic when mortality was high. The ways children mix with each other during a prolonged school closure remain a key uncertainty, likely to be influenced by the severity of the pandemic.”
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