Typhoid Vaccine Could Prevent 90 percent of Typhoid Fever

Typhoid vaccine Vi-TT found 87 percent effective, based on expanded typhoid fever definition

A new typhoid vaccine called Typbar-TCVR, is the first vaccine found safe and effective for children aged under two years of age.

This is important because typhoid fever impacts children in developing countries, where mortality is estimated at 1%, and 3% of individuals become chronic carriers.

Although controlling typhoid fever through improved water quality and sanitation is the long term solution, the infrastructure required to prevent typhoid transmission in affected regions is unlikely in the short term, according to health officials.

Which means, typhoid vaccination is the immediate answer for protecting children.

Officials with the Strategic Advisory Group of Experts (SAGE) on Immunization, which is a committee that advises the World Health Organization (WHO), reviewed the results of a clinical trial and is now recommending Vi-TT as a highly immunogenic typhoid vaccine.

This vaccine, Vi-TT was found to be 87 percent effective, based on an expanded definition of typhoid fever.

The results of this clinical trial were reported in the Lancet.

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This study showed that the Vi-TT was well tolerated, achieved 100% seroconversion of Vi antibody, and stimulated significantly higher geometric mean titres than did than did unconjugated Vi-PS.

Currently licensed typhoid vaccines, such as unconjugated Vi-PS, are either not immunogenic in early childhood or are unsuitable for administration in children younger than 5 years.

The oral live attenuated typhoid vaccine, Ty21a, has been unsuitable for use in children younger than 5 years because of its formulation in capsules, which are difficult for young children to swallow.

Typhoid fever, known as Salmonella enterica serovar Typhi (S Typhi), is responsible for an estimated 20 million infections and 200 000 deaths each year in resource poor regions of the world.

Given the potential efficacy of this new vaccine, SAGE said countries with the greatest burden of typhoid fever and antimicrobial-resistant S. Typhi should be a priority for the vaccine’s introduction, and delivering catch-up immunizations.

This study was funded by The Bill & Melinda Gates Foundation (OPP1084259) and the European Commission FP7 grant “Advanced Immunization Technologies” (ADITEC).

The researchers declared no competing interests. Please see the following link for other SAGE members’ relevant financial disclosures.