Rotavirus disease burden, Nicaragua 2001-2005: defining the potential impact of a rotavirus vaccination program.

BACKGROUND: In October 2006, a rotavirus vaccine was introduced in Nicaragua for routine immunization of all children. We document the baseline diarrheal disease burden in Nicaragua prior to the vaccine program to facilitate future studies to measure vaccine impact. METHODS: We analyzed national data for 2001-2005 on total acute gastroenteritis healthcare visits, hospitalizations, and mortality in Nicaraguan children aged <5 years. RESULTS: Prior to vaccine introduction, by age 5 years, one in four Nicaraguan children required an outpatient consultation, one in 34 were hospitalized, and one in 2487 died from rotavirus-associated diarrhea, representing approximately 41,122 outpatient visits, 4460 hospitalizations, and 60 deaths per year that are preventable through vaccination. Almost half of the total acute gastroenteritis burden was in children <1 year of age. Two distinct seasonal peaks were noted in acute gastroenteritis hospitalizations and deaths. CONCLUSIONS: Existing data sources on all-cause acute gastroenteritis could be useful for establishing diarrhea disease burden and monitoring trends after vaccine introduction. Blunting of winter season peaks in rates of diarrhea, particularly among children aged <1-2 years, would be a useful indicator of impact from rotavirus vaccination.

Uptake of rotavirus vaccine and national trends of acute gastroenteritis among children in Nicaragua.

BACKGROUND: In October 2006, a new rotavirus vaccine was introduced in Nicaragua and was available free to all age-eligible children. We assessed vaccine uptake and trends in acute gastroenteritis (AGE) to assess vaccine impact. METHODS: We analyzed national data from the period 2001-2007 on the total number of AGE episodes and on RotaTeq vaccine dose administration during 2006-2007. RESULTS: After the introduction of RotaTeq, 1-dose vaccine coverage rates rapidly increased to 80% among age-eligible children. During the 2007 rotavirus season, when combined 2- and 3-dose vaccine coverage among children aged 0-11 months was approximately 26%, the total number of AGE episodes among children aged 0-11 months decreased by 23%, compared with a decrease of 6% among unvaccinated children aged 12-59 months. Furthermore, a 12% decrease in the number of all-cause hospitalizations for AGE was noted among children aged 0-11 months, whereas a approximately 5% increase was observed among children aged 12-59 months. CONCLUSIONS: The high rate of vaccination among age-eligible children soon after vaccine introduction in Nicaragua indicates an efficient immunization program. However, in the age group at risk of rotavirus disease, vaccine coverage during the 2007 rotavirus season had yet to reach a level sufficient for making firm conclusions about vaccine impact. Epidemiologic studies to evaluate vaccine effectiveness and ongoing surveillance as vaccine uptake increases will allow a better assessment of vaccine impact.

Association between pentavalent rotavirus vaccine and severe rotavirus diarrhea among children in Nicaragua.

CONTEXT: Pentavalent rotavirus vaccine (RV5), a live, oral attenuated vaccine, prevented 98% of severe rotavirus diarrhea in a trial conducted mainly in Finland and the United States. Nicaragua introduced RV5 in 2006, providing the first opportunity to assess the association between vaccination and rotavirus disease in a developing country. OBJECTIVE: To assess the association between RV5 vaccination and subsequent rotavirus diarrhea requiring overnight admission or intravenous hydration. DESIGN, SETTING, AND PARTICIPANTS: Case-control evaluation in 4 hospitals in Nicaragua from June 2007 to June 2008. Cases were children age-eligible to receive RV5 who were admitted or required intravenous hydration for laboratory-confirmed rotavirus diarrhea. For each case (n = 285), 1 to 3 neighborhood (n = 840) and hospital (n = 690) controls were selected. MAIN OUTCOME MEASURES: Primary outcome was the association of RV5 and rotavirus diarrhea requiring overnight admission or intravenous hydration in the emergency department. Secondary analysis further classified disease as severe and very severe. We computed the matched odds ratio of vaccination in cases vs controls. Vaccine effectiveness was estimated using the formula 1 - matched odds ratio x 100%. RESULTS: Of the 285 rotavirus cases, 265 (93%) required hospitalization; 251 (88%) received intravenous hydration. A single rotavirus strain (G2P[4]) was identified in 88% of the cases. Among cases and controls, respectively, 18% and 12% were unvaccinated, 12% and 15% received 1 dose of RV5, 15% and 17% received 2 doses, and 55% and 57% received 3 doses. Vaccination with 3 doses was associated with a lower risk of rotavirus diarrhea requiring overnight admission or intravenous hydration (odds ratio [OR], 0.54; 95% confidence interval [CI], 0.36-0.82). Of the 285 rotavirus cases, 191 (67%) were severe and 54 (19%) were very severe. A progressively lower risk of severe (OR, 0.42; 95% CI, 0.26-0.70) and very severe rotavirus diarrhea (OR, 0.23; 95% CI, 0.08-0.61) was observed after RV5 vaccination. Thus, effectiveness of 3 doses of RV5 against rotavirus disease requiring admission or treatment with intravenous hydration was 46% (95% CI, 18%-64%); against severe rotavirus diarrhea, 58% (95% CI, 30%-74%); and against very severe rotavirus diarrhea, 77% (95% CI, 39%-92%). CONCLUSION: Vaccination with RV5 was associated with a lower risk of severe rotavirus diarrhea in children younger than 2 years in Nicaragua but to a lesser extent than that seen in clinical trials in industrialized countries.