Complications of varicella requiring hospitalisation before and after the introduction of varicella vaccine in a children's hospital in Taiwan.

We compared the complications of varicella requiringhospitalisation in healthy children before and after theintroduction of varicella vaccine in Taiwan. Overall, themean age of children in post-vaccine period was signi-ﬁcantly older than in the pre-vaccine period, suggestinga change in the epidemiology of varicella in our countryafter the introduction of varicella vaccine.The live attenuated varicella vaccine prevents most ofthe morbidity caused by varicella in children [1] and wasﬁrst commercially available in Taiwan in September1997. However, routine immunisation is not uniformlyrecommended in all practices caring for children andcoverage is not included in health insurance system. Wecompared the complications of primary varicellarequiring hospitalisation in healthy children before andafter the introduction of varicella vaccine to determinethe potential beneﬁts of routine immunisation.A retrospective analysis of hospital records ofchildren less than 15 years of age admitted with ICDcode 052 (varicella) from two study periods wasperformed. The pre-vaccine period was from 1 Septem-ber 1996 to 31 August 1997 and the post-vaccine periodwas from 1 September 1998 to 31 August 1999. Healthychildren with varicella as the primary indication forhospitalisation were included in the study. Varicella-associated complication was deﬁned as a condition orevent occurring within 14 days of onset of varicella towhich varicella zoster virus infection may in some wayhave contributed [4]. Data were statistically analysed.A total of 180 children, 121 in the pre-vaccine and 59in the post-vaccine period were included in the study.Demographics and complications of varicella in hospi-talised children during the pre-vaccine and post-vaccineperiods are shown in Table 1. The mean age of childrenwas 3.23 years in the post-vaccine and 2.51 years in thepre-vaccine period, respectively. Children in the post-vaccine period were signiﬁcantly older than those in thepre-vaccine period (P=0.005). Bacterial skin and softtissue infections were the most frequent complications(56.7%), followed by respiratory and central nervoussystem complications. Our study showed that there wasa marked reduction by 51% in the number of casesadmitted because of varicella associated complicationsin the post-vaccine period.Although varicella is a mild disease of childhood,serious complications requiring hospitalisation and evendeath may occur in healthy children [1, 3,4]. The age ofchildren hospitalised for complications of varicella in thepost-vaccine period was signiﬁcantly higher than that inthe pre-vaccine period. The upward shift in age distri-bution of varicella was observed, which means greatermorbidity because more serious complications are likelyto occur in the adults [1]. Of particular concern is wheninfection occurs in pregnant women.Our hospital served mostly the Taoyuan county,representing 7.5% of the total population of the coun-try. The sales of varicella vaccine in our country wereabout 150,000/year over the past 3 years. Transferringthis number to children aged 1–14 years in this area, lessthan 10% of children had received the vaccine.Currently, there are still about 10% female and 20%male susceptible to varicella in Taipei [5] and the selec-tive use of vaccine will likely increase this proportion inthe future. With the use of varicella vaccine, the circu-lation of wild-type virus decreases leaving many non-immunised children unexposed to natural infection, thusbecoming susceptible adults. If the immunisation rate israised above 90%, the disease burden will decrease in allages [2]. If universal immunisation is not implemented,epidemiological changes are anticipated.The complications of varicella infection in the post-vaccine period did not diﬀer much from those in thepre-vaccine period. Children in the post-vaccine period