Travelers to India May Need Typhoid Vaccination
A new typhoid vaccine could prevent more than half of typhoid infections worldwide, according to a new study published in The Lancet.
This study is a phase 2b trial and provides the first efficacy data for the leading candidate vaccine being considered for widespread use in children under 2 years, who are disproportionately affected by typhoid.
Currently, there are no typhoid vaccines licensed worldwide for use in children under 2 years old.
Typhoid affects between 12.5 and 20.6 million people worldwide in regions with inadequate water quality, contaminated food and poor sanitation, particularly in south Asia and sub-Saharan Africa.
Typhoid is an acute illness, characterized by prolonged fever, headache, nausea, loss of appetite, and constipation or sometimes diarrhoea.
1 in 100 typhoid cases are deadly and approximately 3% of cases become chronic carriers.
Typhoid fever is uncommon in the United States, with only 400 cases reported annually during 2007–2011.
Approximately 90% of U.S. cases occur among persons returning from foreign travel, with 75% of cases had visited India, Bangladesh, or Pakistan.
Typhoid is caused by Salmonella enterica serovar Typhi (S. Typhi bacteria) and is usually treated with antibiotics.
But, antibiotic resistance is increasing.
"Since the 1960s, controlled human infection models have been used to evaluate the efficacy of typhoid vaccine candidates, successfully supporting the development of one of the currently licensed typhoid vaccines Ty21a,” says author Professor Andrew Pollard, Oxford Vaccine Group, University of Oxford.
The WHO's Strategic Advisory Group of Experts is due to consider the use of Vi-conjugate vaccines for the control of typhoid fever in October 2017.
International travelers need to complete their typhoid vaccination at least 1 week before traveling so that the vaccine has time to take effect.
If you were vaccinated in the past, check with your doctor to see if it is time for a booster vaccination, as typhoid vaccines lose effectiveness after several years, according to the CDC.
Most pharmacies offer typhoid vaccinations services. Vaccine discounts can be found here.
In the study led by the University of Oxford (UK), 112 volunteers in the UK were randomly assigned to receive a single dose of the Vi-tetanus toxoid conjugate vaccine (Typbar-TCV; Vi-TT), the pre-existing Vi-polysaccharide vaccine (TYPHIM Vi; Vi-PS), which cannot be given to young children, or a control meningococcal conjugate vaccine (MENVEO).
The authors note that because of the design of the study, the participants were not representative of the populations where typhoid is endemic and where Vi-TT might eventually be deployed.
They note that the most advanced conjugate vaccine, (Typbar-TCV) is licensed in India where it has been shown to elicit robust serum Vi-antibody responses in Indian infants as young as 6 months of age, and an application for pre-qualification has been submitted to WHO.
The study was funded by the Bill & Melinda Gates Foundation and the European Commission. These researchers did not disclose any conflicts of interest.
- Efficacy and immunogenicity of a Vi-tetanus toxoid conjugate vaccine in the prevention of typhoid fever using a controlled human
- National Typhoid and Paratyphoid Fever Surveillance
- SAGE meeting
- Typhoid Fever Vaccination
- The Lancet: Typhoid vaccine proves highly immunogenic, and could halve infection rate
- Typhoid ACIP Vaccine Recommendations
- Vaccinations for the Pediatric Traveler