Single-dose typhoid conjugate vaccine proves long-term effective in children

A single dose of the typhoid conjugate vaccine, Typbar TCV, provides long-lasting effectiveness in preventing typhoid fever in children aged nine months to 12 years, according to a new study led by researchers at the Center for Vaccine. University of Maryland School of Medicine (UMSOM). Development and Global Health (CVD) and led by national partners from the Malawi-Liverpool Wellcome Trust (MLW) Clinical Research Program.

The results of the phase III clinical study were published in The Lancet.

The research team recruited more than 28,000 healthy children in Malawi and randomly assigned about half the group to receive TCV and the other half to receive a meningococcal group A conjugate (MenA) capsular vaccine.

During more than four years of follow-up, 24 children in the TCV group and 110 in the MenA group developed typhoid fever, confirmed by blood culture. This resulted in an effectiveness of 78.3% in the TCV group, with one case of typhoid prevented for every 163 children vaccinated.

TCV was found to be effective in all age groups and during the study period, which ended in 2022. Vaccine effectiveness remained strong, declining by only 1.3% per year.

Typhoid fever causes more than 9 million illnesses and at least 110,000 deaths worldwide each year, mainly in sub-Saharan Africa and Southeast Asia. It is a contagious bacterial infection that results from eating contaminated food or drinks. Symptoms include nausea, fever and abdominal pain which, if left untreated, can be fatal.

“These results have significant implications for identifying the contribution of TCVs in the control and potential elimination of typhoid fever in endemic settings,” wrote the authors of a commentary published in The Lancet parallel to the study.

In May 2023, the Government of Malawi launched a national rollout of TCV in children under 15 years of age. In the future, all children in Malawi will receive TCV at nine months of age as part of the routine immunization schedule.

“The newly published study confirms the long-term impacts of a single TCV injection, even in the youngest children, and offers hope for preventing typhoid in the most vulnerable children,” said Kathleen Neuzil, MD. , MPH, director of cardiovascular diseases, Myron M. Levine, MD, DTPH, professor of vaccinology at UMSOM and co-author of the present study.

“We could not have had a better partner in this endeavor than MLW, whose long-standing excellence in typhoid research and robust surveillance infrastructure made this study possible.”

“CVD’s exceptional record in generating data to accelerate public health decisions continues with this landmark study,” said UMSOM Dean Mark T. Gladwin, MD, vice president for Medical Affairs, University of Maryland, Baltimore, and John Z. and Akiko K. Bowers Distinguished Professor.

“The research could not come at a more critical time, as Malawi and other African countries grapple with climate change, extreme weather events and increased urbanization, which are likely to contribute to increased enteric diseases, notably typhoid.”