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BackgroundVaricella (VZV) is one of the most frequent exanthematic diseases in childhood. In Argentina, around 150,000–180,000 total cases per year 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. The information provided by epidemiological surveillance is essential to evaluate the impact of public health decisions. Our objective was to describe and to compare the epidemiological situation of VZV infections in Argentina in two periods: pre (2010–2014) and post (2016–2017) vaccine introduction in NIS.MethodsDescriptive study. We compared cases and incidence rates (R) of VZV per 100,000 population (global and disaggregated by age) reported to the National Health Surveillance System; in pre (Pre-VV) and post-vaccination (Post-VV) periods. Data analysis of 2015 was excluded since it was considered a transition year.ResultsVaccination coverage for 2015 was 44.7%; 74.4% in 2016 and 75.5% in 2017. 728,392 cases of VZV were notified (R = 362,1) in Pre-VV period and 176,995 cases in Post-VV (R = 220.6), with a global incidence rate reduction of 39% (IC 95% =38.9–39.6; P < 0.001). Both 12–24 months of age and 2–4 years old groups (Pre-VV R 2,253 and Post-VV R 1,077; Pre-VV R 2,400 and Post-VV R 1,165, respectively) showed the greatest reductions in incidence rates (–52.2% [IC 95% 51.3–53] P <0.001 and –51.4% [IC 95% 51–52] P <0.001). Besides, age groups not affected by vaccination (<1 year, 5–9 years, and 10–14 years) presented minor but significant reductions (–49.1% [95% CI 44.5–53.4] P < 0.001; –23% [IC95% 22.4–23.6] P <0.001, and –17% [IC95% 16.4-19] P <0.001, respectively).ConclusionThree years after the implementation of VZV vaccination strategy, a significant incidence rates reduction is recorded, especially in children <5 years old, despite suboptimal coverage. Improving vaccination coverage will likely reflect a greater impact on the burden of disease.Disclosures All authors: No reported disclosures.

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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&lt; 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&lt; 0.001 and -61.7% [95%CI 61.3-62] p&lt; 0.001). Age groups not affected by vaccination (&lt; 1 year, 5-9 years and 10-14 years) presented minor but significant reductions (-56.4% [95%CI 55.6-57.3] p&lt; 0.001; -35% [95%CI 34.5-35.4] p&lt; 0.001; and -28.6% [95%IC 27.6-29.7] p&lt; 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