The Epidemiological Impact of Rotavirus Vaccination Programs in the United States and Mexico

Rotavirus, the most common cause of gastroenteritis among children worldwide, is responsible for approximately 600,000 deaths every year worldwide. Clinical trials of RotaTeq and Rotarix, two commercially generated approved vaccines, have shown a high degree of effectiveness in protecting the most vulnerable individuals against rotavirus infections. RotaTeq and Rotarix are now incorporated into the portfolio of vaccines recommended for regular use by infants in the US and Mexico, respectively. The focus here is to evaluate the impact of vaccine-generated herd immunity, a function of the implementation regimes and coverage policies, on rotavirus transmission dynamics at the population level. In order to evaluate the overall impact of vaccine regimes in the US and Mexico, we develop an age-structured epidemiological model of rotavirus transmission that includes age-specific vaccination rates. This model is parameterized using available epidemiological and vaccine data. Numerical simulations of the parameterized model support the conclusion that reasonable rotavirus vaccination programs can prevent a significant fraction of primary (severe) rotavirus infections in the US and Mexico. Vaccination is likely to have stronger positive impact in Mexico than in the US, because the prevalence of rotavirus infections is higher in Mexico and demographics are distinct in two countries. It is shown that the age distribution of rotavirus cases will shift as a result of vaccination. This shift will be accompanied with decreases in the proportion of primary infections and the change in the distribution of subsequent infections. Effective vaccination regimes tend to increase the average age of both primary and subsequent infections. The observed shifts reduce the average population risk because severity tends to decrease with age.