An international team of health and medical researchers including workers at the WHO, working with economists and modeling specialists, has found that the use of vaccines to prevent or treat disease has saved the lives of approximately 154 million people over the past half-century.

In their study, published in The Lancet, the group used mathematical and statistical modeling to develop estimates for lives saved due to vaccines and then added them together to find the total.

The goal of the team was to evaluate the degree of success of the Expanded Program on Immunization (EPI) launched by the World Health Organization in 1974. The goal of the EPI has been to vaccinate all the children in the world against the most common deadly diseases. At its onset, the list included seven diseases; it has since been expanded to include 14.