Budget impact analysis of multiple varicella vaccination strategies: a Mexico perspective.

A number of live-attenuated varicella vaccines are produced globally that provide protection against the varicella zoster virus. In Mexico, varicella vaccination is not included in the national immunization program and is recommended for use only in high-risk subgroups. We developed a budget impact model to estimate the impact of universal childhood immunization against varicella on the national payer system in Mexico. A scenario of no varicella vaccination was compared to scenarios with vaccination with a single dose at 13 months of age, in alignment with the existing program of immunization with the measles-mumps-rubella vaccine. Nine different vaccination scenarios were envisioned, differing by vaccine type and by coverage. Varicella cases and treatment costs of each scenario were computed in a dynamic transmission model of varicella epidemiology, calibrated to the population of Mexico. Unit costs were based on Mexico sources or were from the literature. The results indicated that each of the three vaccine types increased vaccine acquisition and administration expenditures but produced overall cost savings in each of the first 10 years of the program, due to fewer cases and reduced varicella treatment costs. A highly effective vaccine at 95% coverage produced the greatest cost savings.

Modelling the effect of conjugate vaccines in pneumococcal disease: cohort or population models?

Cohort and population models estimate vaccine impact on disease events, and yield different estimates in countries with different demographic compositions. We compared administration of the new 10-valent pneumococcal Haemophilus influenzae-protein D conjugate vaccine (PHiD-CV) with no vaccination in two countries, the United Kingdom (UK) and Mexico, using two modelling strategies: a cohort model and a population model. The cohort model followed a birth cohort over a lifetime, beginning 10 years after initiation of the vaccine program, when vaccine efficacy steady state had been reached. The population model examined the country-specific population over 1 year, also beginning 10 years after initiation of the vaccine program. Both models included the same age-specific disease rates of meningitis, bacteraemia, pneumonia, and otitis media. The output variables were the numbers of specific events, with and without indirect vaccine effects. Without indirect effects, the cohort and population models produced similar results for both countries (deviation of <20% difference per output measure for most outcomes). The difference between the model types was much greater when indirect vaccine effects were included, especially in Mexico (up to 120% difference). Cohort and population modelling methods produce different results depending on the disease, the intervention, the demographic composition, and the time horizon evaluated. Results from the two model types provide different information about the impact of interventions on events: accumulated vaccine benefit for an individual in a cohort model; vaccine benefit for a whole population at a specific time point in a population model.