Epidemiology and impact of varicella vaccination: A longitudinal study 1994-2011

Abstract

Objective This study examines the epidemiology of varicella infection and the impact of vaccination in a population in Eastern Saudi Arabia. Methods All reported cases of varicella infection from 1994 to 2011 were analyzed. Results A total of 19,577 patients with varicella were reported during the study period, and 8869 were female and 10,248 were male, with a male to female ratio of 1.15:1. Most of the cases were reported in patients between one to four year of age (n = 5625; 29.4%) and five to nine years of age (n = 6614; 34.6%) years of age. The highest numbers of cases were reported in March-May corresponding to the spring time (39.3%) compared with 21.2% in the winter and 25.4% in the summer time. The childhood varicella vaccine was introduced in 1998 and was made mandatory in 2008. The total number of cases decreased from 10,070 in the pre-vaccination period to 1577 cases in the mandatory vaccination period. The incidence rate decreased from 739.8 in 1994 to 355.3 in 1998, to 88.1 in 2011 per 100,000 population (P < 0.0001). Patients less than one year of age constituted 8.3% of cases in 1994-1997 prior to vaccination, 5.4% in 1998-2008 during the initial vaccination phase and 3.4% during the mandatory vaccination period (P < 0.0001). Conclusion The introduction of varicella vaccine resulted in a significant reduction in the incidence rates between 1994 and 2011. © 2013 Elsevier Ltd. All rights reserved.