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The problem
Intervention: Two-dose varicella vaccination recommendation program with increased coverage of second dose, combined with surveillance system optimization
Who it was tested with: Children aged 4-6 years in Chongqing, China; all ages in city affected by policy.
Experience from people who deliver programmes: stories, case studies and lessons learned. Valuable for understanding how and why, and for spotting what to test next, but not a measure of effect.
"The segmented regression model demonstrated that, following the incorporation of varicella into the surveillance system in 2014, there was an upward long-term trend in the reported varicella incidence...Following the implementation of the two-dose VarV recommendation strategy in January 2019, a significant long-term decline trend was observed." The interrupted time series design with segmented regression analysis allows assessment of trend changes before and after the intervention implementation.
Study cannot isolate the effect of vaccination from surveillance improvements. Reported incidence may reflect changes in detection and reporting rather than true population incidence. No comparison with unexposed populations or control regions provided.
Across countries and designs
5 studies · 3 countries
