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

SummaryObjectiveThis study examines the epidemiology of varicella infection and the impact of vaccination in a population in Eastern Saudi Arabia.MethodsAll reported cases of varicella infection from 1994 to 2011 were analyzed.ResultsA 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).ConclusionThe introduction of varicella vaccine resulted in a significant reduction in the incidence rates between 1994 and 2011.