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Impact of the single-dose immunization strategy against hepatitis A in Argentina
Carla Vizzotti1, Jorge González, Angela Gentile
1From the *Ministerio de Salud de la Nación, Av. de 9 de Julio 1925 (C1073ABA); †INEI-ANLIS "Dr. Carlos Malbrán", Av. Vélez Sarsfield 563 (1281); and ‡Sociedad Argentina de Pediatría, C.A.B.A., Argentina.
Insights
Argentina's single-dose hepatitis A vaccine strategy, introduced in 2005, dramatically reduced hepatitis A virus (HAV) infection rates by 88.1%. This intervention has been highly effective in controlling HAV across all age groups.
Area of Science:
- Epidemiology
- Vaccinology
- Public Health
Background:
- Argentina experienced a widespread hepatitis A outbreak in 2003-2004.
- A single dose of hepatitis A vaccine was integrated into the national immunization schedule for 12-month-old children in June 2005.
Purpose of the Study:
- To evaluate the impact of the hepatitis A vaccination program on infection rates.
- To assess the effect of vaccination on severe outcomes like fulminant hepatic failure (FHF) and liver transplantation.
Main Methods:
- Longitudinal analysis of hepatitis A virus (HAV) infection data from 2000-2011.
- Comparison of incidence rates and clinical outcomes between pre-vaccination (2000-2002) and post-vaccination (2006-2011) periods.
- Analysis of notification rates by age group and geographical region.
Main Results:
- A significant decline in HAV infection rates, FHF, and liver transplantation cases was observed starting in 2006.
- Post-vaccination incidence rate decreased by 88.1% compared to the pre-vaccination period (P < 0.001).
- No FHF or liver transplantation cases due to HAV infection were recorded after March 2007; impact was greatest in previously high-incidence areas and young children.
Conclusions:
- The single-dose hepatitis A vaccination strategy has proven highly effective in controlling HAV infection in Argentina.
- Sustained success of this public health intervention necessitates ongoing long-term surveillance.
Background:
After a country wide outbreak occurred during 2003-2004, 1 dose of hepatitis A vaccine was introduced into Argentinian regular immunization schedule for all children aged 12 months in June 2005. The aim of this study was to assess the impact of this novel intervention.
Methods:
A longitudinal analysis was done of hepatitis A virus (HAV) infection rates reported to the National Epidemiological Surveillance System from 2000 to 2011. Occurrence of fulminant hepatic failure (FHF) and liver transplantation cases up to 2011 were also assessed. Incidence rates and clinical impact were compared between pre- and postvaccination periods (2000-2002 vs. 2006-2011). Notification rates were also compared by age groups and geographical regions.
Results:
Since 2006, an abrupt decline was observed in HAV infection rates, as well as in FHF and liver transplantation cases. The mean incidence rate of 7.9/100,000 in the postvaccination period represents a reduction of 88.1% (P < 0.001) when compared with the prevaccination period. Neither FHF nor liver transplantation due to HAV infection were observed since March 2007. Decline in incidence rates was evident in all geographical regions and all age groups but was higher in the prevaccination most affected areas and in young children. Although an absolute decrease was observed for cases and rates in all age groups, since 2006, a higher proportion of cases was observed in people >14 years of age.
Conclusions:
The single-dose vaccination strategy has been highly effective for controlling HAV infection in all age groups till now in Argentina. Long-term surveillance will be critical to document the sustained success of this unique intervention.
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