Elsevier

The Journal of Pediatrics

Volume 173, June 2016, Pages 202-206.e2
The Journal of Pediatrics

Original Article
Strong Additional Effect of a Second Varicella Vaccine Dose in Children in Germany, 2009-2014

https://doi.org/10.1016/j.jpeds.2016.02.040Get rights and content

Objectives

Vaccine effectiveness (VE) of 1 and 2 varicella vaccine doses in children aged 1-4 years in Germany was evaluated to determine the additional effect of a second dose recommended at least 4 weeks after the first dose and before the second birthday.

Study design

To estimate the VE, the proportion of cases vaccinated was compared with the proportion of the population vaccinated using nationwide sentinel surveillance data from 2009-2014 and health insurance claims data covering the period January 2009-March 2014, respectively. A general linear model was used to estimate the OR of vaccination in the cases and the population and the corresponding CIs to observe the stability of the VE estimates over time, and to assess the incremental effectiveness of a second dose.

Results

The overall VE after 1 dose was 86.6% (95% CI: 85.2-87.9), ranging between 94.6% (95% CI: 87.9-97.6) in the first quarter of 2011 and 50.3% (95% CI: 7.3-73.4) in the third quarter of 2013. The overall VE after 2 doses was 97.3% (95% CI: 97.0-97.6), ranging between 99.5% (95% CI: 97.8-99.9) in the second quarter of 2009 and 91.3% (95% CI: 85.7-94.8) in the third quarter of 2013. The incremental VE of 2 doses was 84.6% (95% CI: 81.7-86.9).

Conclusions

The substantially higher VE of 2 varicella vaccine doses compared with 1 dose in young children and the strong additional effect of the second dose support the public health relevance of a 2-dose schedule and the success of the early second vaccine dose.

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.15VE=1PCV1PCV×1PPVPPV=1OR

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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  • Cited by (0)

    Supported by the German Ministry of Health (IIA5-2511NIK002/321-4533-06). The authors declare no conflicts of interest.

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