Varicella, the primary infection with the varicella zoster virus (VZV), is mainly a childhood illness, highly contagious, but usually with an uncomplicated course of disease. Several live-attenuated varicella vaccines are currently licensed in Europe, but only few countries have recommended universal varicella vaccination (UVV) thus far.
Before the introduction of UVV in Germany, more than 90% of all children<12 years of age contracted varicella, with about 2000 hospitalizations per year, including severe neurological and other complications. Germany introduced health-insurance funded, one-dose UVV for all infants 11 to 14 months of age in 2004, and extended the recommendation to a second dose for children 15 to 23 months of age in 2009. The defined primary aim of UVV was the reduction of varicella-associated burden of disease and complications. A further aim was to achieve herd protection effects for risk groups, such as immunocompromised patients, or children too young for vaccination. Various surveillance projects were set up to record the change in coverage and the impact of UVV on the burden of VZV disease, including potential negative effects, such as a shift in the age at infection to higher age due to decreasing VZV circulation. The decrease in VZV ?circulation could also lead to a temporary increase in herpes zoster (HZ), the secondary manifestation of VZV, due to reduced boosting of immunity in persons with previous varicella.
By 2012, varicella vaccination coverage in 2 year-old children in Germany had reached 87% for the first and 64% for the second dose. From 2005 to 2012, varicella cases decreased by 84%, varicella-associated complications in outpatients by 93%, and varicella-associated hospitalizations in children decreased by 60%, including cases with neurological complications. Herd protection effects have been reported for children<11 months of age and for paediatric oncology patients. Thus far, no increase in the absolute numbers of varicella cases in older age groups has been observed.
The impact of UVV on HZ is still uncertain. A consistent increase of HZ-associated hospitalizations was observed in Germany between 1995 and 2012. However, this increasing trend began before UVV was introduced and did not change with the introduction.
In conclusion, UVV in Germany had a strong impact on the burden of varicella disease. Nevertheless, continued long-term surveillance of the effects on both varicella and HZ epidemiology is necessary.