The Impact of an Inactivated Hepatitis A Vaccine with One Dose in Brazil: A Retrospective Time-Series

Abstract

Background: In 2014, a recommended one-dose of inactivated hepatitis A vaccine was included in the Brazilian National Immunization Program targeting children 12–24 months. This decision addressed the low to intermediate endemicity status of hepatitis A across Brazil and the high rate of infection in children and adolescents between 5 and 19 years old. The aim of the study was to conduct a time-series analysis on hepatitis A incidence across age groups and to assess the hepatitis A distribution throughout Brazilian geographic regions. Methods: An interrupted time-series analysis was performed to assess hepatitis A incidence rates before (2010–2013) and after (2015–2018) hepatitis A vaccine program implementation. The time-series analysis was stratified by age groups while a secondary analysis examined geographic distribution of hepatitis A cases. Results: Overall incidence of hepatitis A decreased from 3.19/100.000 in the pre-vaccine period to 0.87/100.000 (p = 0.022) post-vaccine introduction. Incidence rate reduction was higher among children aged 1-4 years old, with an annual reduction of 67.6% in the post-vaccination period against a 7.7% annual reduction in the pre-vaccination period (p < 0.001). Between 2015 and 2018, the vaccination program prevented 14,468 hepatitis A cases. Conclusion: Our study highlighted the positive impact of a recommended one-dose inactivated hepatitis A vaccine for 1–4-years-old in controlling hepatitis A at national level.

Persistence of immunity against hepatitis A in Brazilian children vaccinated with a single dose of inactivated virus vaccine

“…However, despite the low seroprotection against HAV identified in this cohort, the practical effect in Brazil was similar to those described in Argentina 9,10,24 . A sharp decline in the disease followed the start of single dose vaccination in Brazil 8,25–27 . Data from the Brazilian Ministry of Health in 2022 showed a significant downward trend in the incidence of Hepatitis A in children under 15 years of age in all regions of the country between 2014 and 2021 25 .…”

“…Adding to the fact that there were no cases of hepatitis A in the district in children under 9 years of age after the vaccination program was started, 30 it is possible to state that this strategy is successful, as also pointed out by other authors. 8,26,27 However, a lower prevalence of children with immunological memory was identified compared to studies with less prolonged observation. 11,12,23 Therefore, it is important to monitor reporting data on new hepatitis A cases and to schedule new cohort assessments of children vaccinated with a single dose, to assess the need for a booster dose in the future.…”

“…9,10,24 A sharp decline in the disease followed the start of single dose vaccination in Brazil. 8,[25][26][27] Data from the Brazilian Ministry of Health in 2022 showed a significant downward trend in the incidence of Hepatitis A in children under 15 years of age in all regions of the country between 2014 and 2021. 25 Despite failures in vaccination coverage in recent years, the public program of universal childhood vaccination against HAV in Brazil is achieving its objectives.…”

“…25 Despite failures in vaccination coverage in recent years, the public program of universal childhood vaccination against HAV in Brazil is achieving its objectives. 8,[25][26][27] This can be supported by the important drop in the incidence of the disease. 8,[25][26][27] As only children under 5 years of age were vaccinated, the herd immunity effect explains the drop in incidence also in other age groups, as already demonstrated, for example, in Israel.…”

“…8,[25][26][27] This can be supported by the important drop in the incidence of the disease. 8,[25][26][27] As only children under 5 years of age were vaccinated, the herd immunity effect explains the drop in incidence also in other age groups, as already demonstrated, for example, in Israel. 28 This work has some limitations.…”