Vaccinations for Diarrhea in Mexico

Diarrhea can kill children and is often caused by rotavirus. Read the abstract below, and answer the questions that follow.

"Methods: We obtained data on deaths from diarrhea, regardless of cause, from January 2003 through May 2009 in Mexican children under 5 years of age.

We compared diarrhearelated mortality in 2008 and during the 2008 and 2009 rotavirus seasons with the mortality at baseline (2003-2006), before the introduction of the rotavirus vaccine. Vaccine coverage was estimated from administrative data.

Results: Diarrhea-related mortality fell from an annual median of 18.1 deaths per 100,000 children at baseline to 11.8 per 100,000 children in 2008 (rate reduction, 35%; 95% confidence interval [CI], 29 to 39; P 6 0.001). . . . Mortality among unvaccinated children between the ages of 24 and 59 months was not significantly reduced. The reduction in the number of diarrhea-related deaths persisted through two full rotavirus seasons (2008 and 2009).

Conclusions: After the introduction of a rotavirus vaccine, a significant decline in diarrhea-related deaths among Mexican children was observed, suggesting a potential benefit from rotavirus vaccination."

a. State the death rate before vaccine and the death rate after vaccine. What was the change in deaths per 100,000 children? From the given p-value, can you reject the null hypothesis of no change in death rate?

b. Would you conclude that the vaccine was effective? Why or why not?

(Source: R. Vesta et al. 2010. Effect of rotavirus vaccination on death from childhood diarrhea in Mexico. New England Journal of Medicine 62, 299-305.)