Diarrhea is among the leading infectious killers of children worldwide, second only to pneumonia in its contribution to child mortality. Rotavirus, the most important cause of diarrhea, is responsible for an estimated 527,000 deaths1
and 138 million episodes of diarrhea2
in the world each year. While oral rehydration programs have been successful in reducing the mortality from diarrhea, the overall incidence of diarrhea has not declined since the 1950’s.3
The introduction of two rotavirus vaccines in 2006 offered new tools to prevent both diarrhea episodes and diarrhea-related deaths.
In Nicaragua, rotavirus had been detected in 28% of children who received care for diarrhea.4
As found elsewhere in the developing world, Nicaraguan children historically acquired their first rotavirus infection at a young age; by one year, 90% had developed symptomatic rotavirus diarrhea or had evidence of seroconversion.5
The highest peak of rotavirus transmission in Central America occurs during the dry season (Quarter 1, January to March).6
In October, 2006, Nicaragua became the first nation eligible for funding by the GAVI Alliance to begin universal infant rotavirus immunization. Nicaraguan infants receive the pentavalent rotavirus vaccine (Rotateq®, Merck) through the national Expanded Program on Immunization at the ages of 2,4, and 6 months. The rotavirus vaccine was made available to all infants who were born on or after August, 2006. Children born before this time were not eligible to receive the vaccine. By the end of 2007, the local health ministry in León, Nicaragua, reported that the vaccine’s coverage in the state was 98% for receipt of the first dose, 93% for receipt of the second dose, and 77% for receipt of all three doses. The coverage for the complete series in León’s 10 municipalities ranged from 61% to 82%.
While the pentavalent rotavirus vaccine was shown to prevent 98% of severe rotavirus gastroenteritis in clinical trials, these trials occurred primarily in Europe and the United States.7
It is unclear whether the rotavirus vaccines will perform as well in the developing world, due to factors such as the distribution of rotavirus genotypes8–11
, the simultaneous use of the oral polio vaccine12–14
, a higher prevalence of malnutrition15–17
and breastfeeding, 18–21
and possible inadequate vaccine storage conditions. The monovalent rotavirus vaccine provided only 49% efficacy against severe rotavirus gastroenteritis in a recent clinical trial in Malawi, significantly lower than the vaccine's efficacy in upper-income countries.22,23
Similarly, a case-control study based in four Nicaraguan hospitals found the pentavalent rotavirus vaccine to be 58% effective against severe rotavirus diarrhea.24
To quantify the impact of the rotavirus immunization program in Nicaragua, we compared the incidence of all-cause diarrhea and diarrhea-related mortality in children before and after the immunization program using data collected by the local health ministry in the state of León, Sistemas Locales de Atención Integral a la Salud (SILAIS). By examining the impact over several years after the introduction of the immunization program, we reduced the effect of possible annual variation of rotavirus transmission.