Original ArticleStrong Additional Effect of a Second Varicella Vaccine Dose in Children in Germany, 2009-2014
Section snippets
Statistical Analyses of the VE
The VE was estimated according to the screening method by calculating the OR as below, where PCV denotes the proportion of cases vaccinated and PPV denotes the proportion of the population vaccinated.15
The OR was then fitted in a generalized linear model with a binomial error structure.16 The generalized linear model was used to estimate the VE and the corresponding 95% CIs for 1 and 2 doses over the entire period and stratified by the year and quarter to observe the
Results
After the stepwise validation procedure, the total number of remaining monthly observations was 31 288, with 8153 reported varicella cases at age 1-4 years. Of those, 403 (4.9%) cases were vaccinated only once, and 285 (3.5%) were vaccinated twice (Table I). One-dose varicella vaccination coverage decreased from 45.2% in the first quarter of 2009 to 18.8% in the first quarter of 2014 among children aged 1-4 years (Table II; available at www.jpeds.com). In the same period, 2-dose varicella
Discussion
This large-scale and nationally representative study of 2-dose varicella VE after the introduction of the routine second varicella vaccine dose in Germany revealed a 2-dose VE above 95% and an incremental effectiveness of 84.6% compared with a single dose. These data demonstrate that a childhood vaccination schedule with 2 doses in the second year of life is effective in protecting children against varicella. The results of the present study are comparable with the findings of pre- and
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Supported by the German Ministry of Health (IIA5-2511NIK002/321-4533-06). The authors declare no conflicts of interest.