There are as many as 270,000 deaths from typhoid fever globally each year, with the largest health burden concentrated in developing countries with poor water quality and sanitation.
Public health interventions have the potential to reduce this number.
With a new $609,150 grant from the Bill & Melinda Gates Foundation, Dr. Virginia Pitzer, assistant professor at the Yale School of Public Health, will develop statistical and mathematical models to estimate the cost-effectiveness of Vi-conjugate vaccines against typhoid fever. This vaccine uses the typhoid Vi antigen, which is the basis of the current typhoid shot, and attaches it to another antigen (e.g., tetanus toxoid) to stimulate a more robust immune response, leading to greater and longer lasting protection from the vaccine. There are a number of vaccine candidates currently in development.
The models will account for both the direct protection received by people who get the vaccines as well as the indirect protection that comes from reductions in the transmission of the bacteria in the population, Dr. Pitzer said. There are between 12 and 27 million typhoid infections annually.
The research will also examine what factors are most important in determining whether typhoid vaccinations will be cost effective in different countries. They will conduct budget impact analyses to determine the affordability of the vaccines, and the results will guide decisions on how best to introduce Vi-conjugate vaccines into local or national immunization programs.
“Our preliminary modeling results suggest that Vi-conjugate vaccines are likely to be cost-effective in medium and high incidence settings, but it will be difficult to eliminate typhoid through vaccination alone,” Dr. Pitzer said. “We also plan to look at how other interventions, such as those targeted toward improving water quality and sanitation, can also help to reduce the burden of typhoid in endemic countries.”
Typhoid is a contagious virus that can cause inflammation of the stomach and intestines. Symptoms include severe diarrhea, often with vomiting, fever and abdominal pain. Infants and young children are most likely to get typhoid and can become severely dehydrated and need to be hospitalized from the infection.
Dr. Pitzer said that the support of the Gates Foundation increases the public health relevance of the research and “opens doors” to potential collaborators and the policymakers who will decide whether and how these vaccines will be used.
Dr. Pitzer’s work focuses on mathematical modeling of the transmission dynamics of infections and how interventions such as vaccination and improvements in sanitation affect disease transmission at the population level. In addition to typhoid, Dr. Pitzer works on rotavirus, cholera and respiratory syncytial virus.