Effects of school breaks on influenza-like illness incidence in a temperate Chinese region: an ecological study from 2008 to 2015

Chu, Yanhui; Wu, Zhenyu; Ji, Jiayi; Sun, Jingyi; Sun, Xiaoyu; Qin, Guoyou; Qin, Jingning; Xiao, Zheng; Ren, Jian; Qin, Di; Zheng, Xueying; Wang, Xi-Ling

The finding that IRRs of schoolchildren aged 5-14 to adults increased significantly in winter breaks is inconsistent with findings of influenza activities in Chile. 10 Although ILI incidence rates of age group 5-14 had been reduced by 26.3% (95% CI 24.9% to 27.7%) after entering winter breaks in 2008-2015, reductions in ILI incidence rates for adults' groups were even larger and thus resulted in increased IRRs of age group 5-14 to adult. In addition to different strains of influenza circulating in a certain year, there could be many other human behaviour factors playing a role in regulating seasonal age-specific ILI visits in China. For example, under pressure of final examinations before winter *Small p values indicate that the IRR for the period before the break is significantly higher than that for the period during the break (or the IRR for the period during the break is significantly higher than that for the period after the break). ILI, influenza-like illness; IRR, incidence rate ratio.