The oral Ty21a vaccine prevented one-third to one-half of typhoid cases in the first two years after vaccination, but had no benefit in the third year.  The injectable Vi polysaccharide vaccine prevented about two-thirds of typhoid cases in the first year and had a cumulative efficacy of 55% by the third year. Neither vaccine is effective in children under 5 years old.  Vi-rEPA vaccine , a new conjugate form of the injectable Vi vaccine, may be more effective and prevents the disease in many children under the age of 5 years.  In a trial in 2-to-5-year-old children in Vietnam, the vaccine had more than 90 percent efficacy in the first year and protection lasted at least 4 years. 
Since the 1990s there have been two typhoid fever vaccines recommended by the World Health Organization. The ViPS vaccine is given via injection, while the Ty21a is taken through capsules. It is recommended only people 2 years or older be vaccinated with the ViPS vaccine and requires a revaccination after 2–3 years with a 55–72% vaccine efficacy. The alternative Ty21a vaccine is recommended for people 5 years or older, and has a 5-7-year duration with a 51–67% vaccine efficacy. The two different vaccines have been proven as a safe and effective treatment for epidemic disease control in multiple regions.