1392. Evaluation of the Impact of a Single-dose Hepatitis A Vaccination in Brazil: a time-series analysis

BACKGROUND: Brazil has transitioned from an intermediate to low hepatitis A virus endemic country, increasing the risk of severe Hepatitis A (HepA) disease. To control transmission, the HepA vaccine, MSD, was introduced in the National Childhood Immunization Program (NIP) in 2014 for children aged 12-24 months and extended to children under 5 years old in 2017. We evaluated the impact of the vaccination on the HepA incidence, associated healthcare resource utilization (HCRU), and costs. METHODS: We conducted an observational, retrospective study using Brazilian National Public Health Data (DATASUS). An interrupted time-series analysis was conducted for incidence rates (IR) of laboratory- or clinically-confirmed Hep A cases. Using a negative binomial regression model, we assessed changes in annual HepA IR between pre- (2010-2013) and post- (2015-2018) HepA vaccination periods and compared to predicted counterfactual rates without HepA vaccination. We compared HCRU and cost of Hep A-associated hospitalizations and outpatient procedures between pre- and post- HepA vaccination periods. RESULTS: Between 2010 and 2018, 32,295 Hep A cases occurred across all ages. Among the NIP target children aged 1-4 years, HepA vaccination was associated with an immediate HepA IR decrease (-52,5% of level change) and with a decrease in slope (-7.7% vs -67.6% per year for pre- and post-periods, respectively, Figure 1). We observed a similar trend in non- HepA vaccination target children aged 5-14 years with -57.1% of level change and slope change from -3.4% (pre- HepA vaccination) to -53.7% (post- HepA vaccination) per year (Table 1). Across all age groups, 14,468 Hep A cases were averted when compared to predicted counterfactual rates (Table 2). Overall, HepA-related hospitalization rate dropped 64% after NIP introduction of vaccination resulting in a cost reduction of 55%. The total number of outpatient procedures claimed among HepA-diagnosed patients reduced 18% with 42% cost reduction. Figure 1: time-series analyses of Hepatitis A incidence rate (IR) for NIP target population. Monthly number of hepatitis A cases observed over the study period (black line). Predicted trend based on the pre- HepA vaccination (red line) and post- HepA vaccination (blue line) monthly cases [Image: see text] Table 1: Time-series analysis of the impact of the hepatitis A vaccination on the incidence rate level of change, according to age group [Image: see text] Table 2: Number of observed, predicted counterfactual, and averted hepatitis A cases in the post- HepA vaccination period (2015-2018), according to age group. [Image: see text] CONCLUSION: In Brazil, the single-dose hepatitis A vaccine childhood program effectively reduced the Hepatitis A incidence, HCRU and associated-costs in vaccinated and in some non-vaccinated age groups. DISCLOSURES: Ana Luiza Bierrenbach, MD, MSc, PhD, MSD Brazil (Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support) Yoonyoung Choi, PhD, MS, RPh, Merck (Employee) Paula M. Batista, BSc, MSD Brazil (Employee) Fernando Serra, MD, MSD Brazil (Employee) Cintia Parellada, MD, PhD, MSD Brazil (Employee) Guilherme Julian, BSc, MSc, IQVIA (Employee)MSD (Consultant, Research Grant or Support) Karina Nakajima, BSc, PhD, IQVIA (Employee)MSD (Consultant, Research Grant or Support) Thais Moreira, MD, MSc, MSD Brazil (Employee)