title: Safety of Zostavax™--a cohort study in a managed care organization.
abstract: BACKGROUND
  Zostavax™ is a live, attenuated varicella-zoster virus vaccine indicated for the prevention of herpes zoster (shingles). An observational post-licensure (Phase IV) study was conducted at Kaiser Permanente Northern California (KPNC), a US managed care organization, to assess the safety of zoster vaccine in people 60 years of age or older, vaccinated in routine medical care.
  
  
  METHODS
  We performed a cohort study, comparing rates of clinical events resulting in hospitalizations or emergency department visits in a 42-day risk time period immediately following vaccination with rates in the same cohort in a subsequent comparison time period. The study data were reviewed and interpreted by an external safety review committee of 3 independent experts.
  
  
  RESULTS
  Approximately 29,000 people ≥ 60 years of age were vaccinated with zoster vaccine from July 2006 to November 2007. Of the 386 comparisons performed for the main analysis, 4 had an increased relative risk with a nominal p-value ≤ 0.05. After medical records review, the timing of these conditions and procedures was found to be often prior to vaccination, and no clear increase in health events was observed in the risk period following vaccination compared to later. Persons receiving zoster vaccine appeared to be in their optimal health at the time of vaccination, which led to an apparent protective effect of the vaccine for some health outcomes, due to the study design.
  
  
  CONCLUSIONS
  There was no evidence of a safety concern for zoster vaccine.
authors.affiliation: Kaiser Permanente Vaccine Study Center, Oakland, CA, USA. roger.baxter@kp.org
authors.forename: Roger
authors.initials: R
authors.lastname: Baxter
authors.forename: Trung Nam
authors.initials: TN
authors.lastname: Tran
authors.forename: John
authors.initials: J
authors.lastname: Hansen
authors.forename: Michael
authors.initials: M
authors.lastname: Emery
authors.forename: Bruce
authors.initials: B
authors.lastname: Fireman
authors.forename: Joan
authors.initials: J
authors.lastname: Bartlett
authors.forename: Ned
authors.initials: N
authors.lastname: Lewis
authors.forename: Patricia
authors.initials: P
authors.lastname: Saddier
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002140:California; D015331:Cohort Studies; D005260:Female; D006562:Herpes Zoster / Q000517:prevention & control; D053061:Herpes Zoster Vaccine / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008329:Managed Care Programs; D008875:Middle Aged; D011358:Product Surveillance, Postmarketing; D012189:Retrospective Studies; D018570:Risk Assessment; D014611:Vaccination / Q000706:statistics & numerical data; D014613:Vaccines, Attenuated / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D053061:Herpes Zoster Vaccine; D014613:Vaccines, Attenuated