Impact of universal varicella vaccination in Navarre, 2006-2010

Background. In 2007 universal varicella vaccination was introduced in the childhood immunization schedule of of Navarre. The aim of this study is to evaluate the impact of this measure on the incidence of varicella in both vaccinated cohorts (direct effect) and in the unvaccinated (indirect effect). Material and methods. Varicella is a notifiable disease. We analyzed the annual incidence by age groups between 2006 and 2010. Hospital admissions with varicella or complicated varicella as the principal diagnosis were obtained from the minimum basic data set on hospital discharges for the years 2006 to 2009. Results. The incidence of varicella has decreased by 93.0%, from 8.04 cases per 1,000 inhabitants in 2006 to 0.56 per 1,000 inhabitants in 2010 (p<0,0001). In children from 1 to 6 years (vaccinated cohorts), the incidence of varicella has fallen by 96.3%. In the cohorts vaccinated at 10 and 14 years, a decrease of 93.6% can also be observed in children from 10 to 14 years, and of 85.0% in those of 15 to 19 years. In the unvaccinated age groups we can observe falls of 88.2% in children under one year, of 73.3% in those of 7 to 9 years, and of 84.6% in people over 20 years. In 2006 there were 25 hospital admissions due to varicella in Navarre and in 2009 this figure decreased to 7. The rate of admissions fell by 73%. Conclusion. The introduction of universal varicella vaccination in Navarre has resulted in a rapid and very steep reduction of the incidence of varicella in both vaccinated and unvaccinated people.