A new vaccine for typhoid control

The Lancet
Jan 13, 2018 Volume 391 Number 10116 p95-178

A new vaccine for typhoid control
The Lancet
Last week, WHO announced prequalification of the first conjugate vaccine to prevent typhoid (Typbar TCV, manufactured by Bharat Biotech, India) after the publication of randomised controlled trials, including that by Celina Jin and colleagues in The Lancet on Sept 28, 2017. WHO has decided that Typbar TCV was successfully assessed for quality, safety, and efficacy, and it is now approved for distribution by UN agencies. Already in use in India and Nepal in babies older than 6 months, the vaccine is to be licensed for use in infants younger than 2 years. Currently, licensed typhoid vaccines are either not immunogenic in early childhood (parenteral Vi capsular polysaccharide vaccine) or are unsuitable for administration in young children because of formulation in capsules (oral live attenuated typhoid vaccine, Ty21a).

There are an estimated 12·5–20·6 million cases of typhoid worldwide each year, with a mortality rate of one per 100 cases. Typhoid is caused by Salmonella enterica serovar Typhi (S Typhi bacteria), which is spread by poor sanitation conditions, contaminated food, and poor quality water. Effective treatment with antibiotics is increasingly impeded by resistance to antibiotics. Children are the most susceptible group, but, without a vaccine, widespread immunisation programmes for young infants have not been possible.

Gavi, the Vaccine Alliance, has confirmed allocation of US$85 million of funding to roll out the vaccine in south Asia, sub-Saharan Africa, and beyond between 2019 and 2020. Priced by Bharat Biotech at US$1-1·50 per dose, Typbar TCV will potentially protect millions of children and greatly reduce mortality from typhoid. Other UN agencies including UNICEF are now able to procure the vaccine, in line with the WHO Strategic Advisory Group of Experts’ recommendation to roll out to all infants over 6 months of age in at-risk endemic countries. Once a successful programme of prevention is in place, phase 3 and 4 trials will lead to a better understanding of long term efficacy and side-effects, and to further refine future strategies of immunisation.