Safety of zoster vaccine in adults from a large managed-care cohort: a Vaccine Safety Datalink study
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Abstract. Objectives. The aim of this study was to examine a large cohort of adults who received the zoster vaccine for evidence of an increased risk of prespecified adverse events requiring medical attention. Design. Two self-comparison approaches, including a case-centred approach and a self-controlled case series (SCCS) analysis were used. Setting. Eight managed-care organizations participating in the Vaccine Safety Datalink project in the United States. Subjects. A total of 193 083 adults aged 50 and older receiving a zoster vaccine from 1 January 2007 to 31 December 2008 were included. Main outcome measures. Prespecified adverse events were identified by aggregated International Classification of Diseases, Ninth Revision (ICD-9) codes in automated health plan datasets. Results. The risk of allergic reaction was significantly increased within 1-7 days of vaccination [relative risk = 2.13, 95% confidence interval (CI): 1.87-2.40 by case-centred method and relative rate = 2.32, 95% CI: 1.85-2.91 by SCCS]. No increased risk was found for the following adverse event groupings: cerebrovascular events; cardiovascular events; meningitis; encephalitis; and encephalopathy; and Ramsay-Hunt syndrome and Bell's palsy. Conclusions. The results of this study support the findings from the prelicensure clinical trials, providing reassurance that the zoster vaccine is generally safe and well-tolerated with a small increased risk of allergic reactions in 1-7 days after vaccination.