1382. Varicella Burden Disease in Argentina: 4 Years after National Vaccination Strategy

Abstract Background In Argentina, around 150,000-180,000 total Varicella (VZV) cases per year (c/y) are registered; however, underreport exists and some 400,000 cases are estimated to occur annually. Varicella vaccine (VV) was included in the National Immunization Schedule (NIS) in 2015, with a 1-dose schedule administered at 15 months-of-age. We aimed to describe and to compare the epidemiological situation of VZV infections in Argentina in two periods: pre (2010-2014) and post (2016-2018) vaccine introduction in NIS. Global Incidence rates and vaccine coverages Incidence rates (age groups) Methods Before-and-after study comparing cases and incidence rates (100,000) of varicella reported to the National Health Surveillance System between pre-vaccination period (Pre-VV) and post-vaccination (Post-VV), excluding year of intervention (2015) since it was considered a transition year. Epi Info 7 was used for data analysis. Results Vaccination coverage (VC) for 2015 was 44.7%; 74.4% in 2016; 76.8% in 2017 and 81% in 2018 (Figure 1). 728,392 cases of VZV were notified (R=363.1) in Pre-VV period and 222,305 cases in Post-VV (R=180.7), with a global incidence rate reduction of 49% (95%CI= 40.9-56.2; p< 0.001). Both 12-24 months of age and 2-4 years old groups (Pre-VV R=2,253 and Post-VV R=900; Pre-VV R=2,399 and Post-VV R=875, respectively) showed the greatest reductions in incidence rates (-59.3% [95%CI 58.7-60] p< 0.001 and -61.7% [95%CI 61.3-62] p< 0.001). Age groups not affected by vaccination (< 1 year, 5-9 years and 10-14 years) presented minor but significant reductions (-56.4% [95%CI 55.6-57.3] p< 0.001; -35% [95%CI 34.5-35.4] p< 0.001; and -28.6% [95%IC 27.6-29.7] p< 0.001 respectively) (Figure 2). Conclusion A decreasing trend in VZV number of cases and incidence rates was observed, especially in children less than 5 years old, despite suboptimal VC. The reduction of VZV cases in non-vaccinated age groups could be related to a decline in the transmission risk. Improving VC will likely reflect a greater impact on the burden of disease. Disclosures All Authors: No reported disclosures