2301. Increased Risk of Varicella-Associated Hospitalizations Among Adult Immigrants From Temperate and Tropical Countries After the Introduction of a Childhood Varicella Vaccination Program in Quebec, Canada

Background Varicella zoster virus (VZV) hospitalizations are an uncommon, severe and costly consequence of VZV. Childhood VZV vaccination leads to decreased VZV rates across all age groups through herd immunity but increases the age of VZV acquisition and the potential risk of severe VZV in non-immune adults. A large proportion (~15%) of young adult immigrants from tropical regions are susceptible to VZV due to different transmission dynamics in their countries of origin and lack of vaccination. We aimed to describe the impact of the childhood VZV program introduced in 2006 in Quebec on VZV hospitalizations in immigrants and nonimmigrants. Methods A population-based cohort of all medically-attended VZV cases in Quebec, Canada (1996–2014) were identified in administrative health databases and linked to immigration data. VZV-attributable hospitalizations included those with primary or secondary ICD-9 or ICD-10 codes for VZV. Overall age-standardized and age-specific rates of hospitalizations were calculated during pre- (1996–98), private (1999–2005) and public vaccination (2006–14) periods and by immigrant status and pregnancy. Relative risk (RRI-NI) and 95% CI for immigrants vs. nonimmigrants were estimated. Results 5873 hospitalizations occurred among 230,052 VZV cases. Hospitalization rates decreased dramatically in the pre to public vaccination period (6.6 to 1.3/100,000 population); however, the proportion of hospitalized varicella cases increased from 1.7% to 3.9% (P < 0.01). Immigrants only accounted for 3.6% of hospitalizations (N = 213) however, the proportion of all hospitalizations among immigrants increased in the pre- vs. public-vaccination periods in those aged 10–19 years (2.9% to 13.7%) and 20–39 years (8.8% to 22.7%). The RR was higher in these age groups in the public vaccination period [RRI-NI 1.96 and RRI-NI 1.67] (Table 1). Adults (>20 years) accounted for 52% (CI: 45–59%) and pregnant women 18% (13–25%) of all hospitalizations among immigrants compared with only 14% (13–15%) and 1.6% (1.3–2.0%) in nonimmigrants, respectively. Conclusion Young adult and pregnant immigrants bore a disproportionate burden of VZV hospitalizations after the introduction of childhood VZV vaccination. Susceptible immigrant adults would benefit from targeted VZV vaccination. Disclosures All authors: No reported disclosures.