2481. Impact of Sex and Race/Ethnicity on the Effectiveness of Live Zoster Vaccine

BACKGROUND: Zostavax™, a live zoster vaccine licensed as 1 dose, is indicated in the United States for the prevention of herpes zoster (HZ) in people 50 years or older. Real-world vaccine effectiveness (VE) and duration of protection are being evaluated in an ongoing study. Compared with randomized clinical trials, this large observational study includes a more diverse population and offers a unique opportunity to assess VE across sex and race/ethnic groups. METHODS: Kaiser Permanente Northern California members enter the ongoing cohort study when age-eligible for zoster vaccine, starting in 2007. Incident HZ is defined as a new HZ diagnosis accompanied by an antiviral prescription or a positive varicella-zoster virus test, with no HZ diagnosis in the preceding 12 months. VE by sex and race/ethnicity was estimated using Cox regression models controlling for age and adjusting for healthcare use, comorbidities and immunocompromise status. RESULTS: During 2007–2014, 1,355,720 individuals entered the study, including 724,283 (53.4%) females. Among the unvaccinated, the incidence rate of HZ was 7.5 and 10.2 cases per 1,000 person-years (PY) among males and females, respectively. VE was 51.6% [95% CI: 49.2, 53.9] in males and 47.7% [45.8, 49.6] in females. The study included 818,361 (60.4%) Whites, 208,248 (15.4%) Asian/Pacific Islanders, 171,949 (12.7%) Hispanics, 98,914 (7.3%) African Americans, and 58,248 (4.3%) with Other/Unknown race/ethnic group. HZ incidence among the unvaccinated was highest among Hispanics (10.1 per 1,000 PY) and lowest among African Americans (6.7 per 1,000 PY). VE was somewhat higher among Hispanics (57.0% [52.7, 61.0]) compared with Whites (48.1% [46.3, 49.9], Asian/Pacific Islanders (49.7% [46.0, 53.3]), and African Americans (50.5% [42.3, 57.6]). CONCLUSION: Overall, VE against HZ was generally similar across sex and race/ethnic groups, except for a somewhat higher VE among Hispanics. This small difference in VE may be due to differences in time since vaccination, since VE tends to wane over time (e.g., average follow-up was 2.2 years for vaccinated Hispanics vs. 2.8 for Whites, resulting in Hispanics having relatively more follow-up closer to vaccination when VE is higher). Longer study follow-up may help to interpret these findings. DISCLOSURES: M. A. Marks, Merck and Co. Inc.: Employee and Shareholder, Salary. P. Saddier, Merck and Co. Inc.: Employee and Shareholder, Salary. N. P. Klein, Sanofi Pasteur: Investigator, Research grant. Merck: Investigator, Research grant. GSK: Investigator, Research grant. Pfizer: Investigator, Research support. Protein Science: Investigator, Research grant. MedImmune: Investigator, Research grant. Dynavax: Research Contractor, Grant recipient.