Single-Dose Universal Hepatitis A Immunization in Argentina: Low Viral Circulation and High Persistence of Protective Antibodies Up to 4 Years.

BACKGROUND: Single-dose hepatitis A virus (HAV) vaccination was implemented in all Argentinean children aged 12 months in 2005. Between 2005 and 2011, a dramatic decline was observed in HAV infection rates, fulminant hepatitis, and liver transplantation. This study assessed current viral circulation and estimated protective antibody persistence 4 years after vaccination. METHODS: Prevalence of prevaccination anti-HAV antibodies in 12-month-old children was evaluated as an indirect estimation of viral circulation (Group A). Seroprevalence was also measured in 5-year-old children who received 1 dose of HAV vaccine at 1 year of age (Group B). Blood samples were tested for immunoglobulin (Ig)G anti-HAV antibodies (seroprotection = ≥10 mIU/mL). All Group A-positive samples were tested for IgM anti-HAV antibodies to identify recent infections. Logistic regression analysis was done to evaluate associations between demographic and socioeconomic variables and seroprotection. RESULTS: Of 433 children from Group A, 29.5% (95% confidence interval [CI], 25.2-33.8) were positive for IgG anti-HAV antibodies with a geometric mean concentration (GMC) of 6.17 mIU/mL (95% CI, 5.33-7.15 mIU/mL); all IgM anti-HAV were negative. From 1139 in Group B, 93% (95% CI, 91.7-94.6) maintained seroprotection with a GMC of 97.96 mIU/mL (95% CI, 89.21-107.57 mIU/mL). Kindergarten attendance was associated with seroprotection in Group B (odds ratio [OR], 2.0; 95% CI, 1.26-3.3). In contrast, high maternal educational level was associated with a lack of seroprotection in this group (OR, .26; 95% CI, .09-.8). CONCLUSIONS: Single-dose, universal hepatitis A immunization in infants resulted in low HAV circulation and persistent immunologic protection up to 4 years in Argentina. Variables associated with presence or absence of seroprotection in vaccinated children could be related to differences in hygiene habits in settings with residual viral circulation.

Economic analysis of the single-dose immunization strategy against hepatitis A in Argentina.

BACKGROUND: Vaccination against hepatitis A (HA) was carried out only as part of a limited outbreak control strategy in Argentina until June 2005, when universal immunization in infants was introduced into the national immunization calendar. A single-dose strategy was chosen instead of the standard two-dose schedule used elsewhere. This study aimed to estimate preventive, medical, and non-medical costs related to HA and to compare these costs in the periods before and after mass vaccination. METHODS: A retrospective analysis estimated treatment costs of HA and unspecified hepatitis cases reported to the National Health Surveillance System from 2000 to 2010. Costs related to immunization, fulminant hepatitis (FH), liver transplantation, and death were projected as well. Using a social perspective and a healthcare system perspective, costs in two 5-year periods were compared: 2000-2004 versus 2006-2010. Finally, we evaluated the impact of different discount rates, FH risk, and exclusion of unspecified hepatitis cases in the sensitivity analysis. RESULTS: Total HA and unspecified hepatitis cases decreased from 157,871 in 2000-2004 to 17,784 in 2006-2010. Medical and non-medical costs decreased from US$11,811,600 and US$30,118,222 to US$1,252,694 and US$4,995,895 in those periods, respectively. Immunization costs increased from US$6,506,711 to US$40,912,132. Total preventive, medical, and non-medical costs decreased from US$48,436,534 to US$47,160,721, representing a 2.6% reduction in total costs between the two periods. When a healthcare system perspective was considered or unspecified hepatitis cases were excluded, total costs were 130.2% and 30.8% higher in 2006-2010 than in the previous period, respectively. CONCLUSION: After implementation of the universal single-dose vaccination against HA in infants in Argentina, an impressive decline was observed in HA cases, with a decrease in medical and non-medical costs in the first 5 years. The single-dose strategy, which is simpler and less expensive than the standard two-dose scheme, can be a good alternative for future vaccination policies in other countries where HA is endemic.