Towards Deeper Understanding of the Typhoid Conjugate Vaccine

Dr. Priyanka Patel studies the typhoid conjugate vaccine, which has been introduced into the immunization schedule in Malawi.

Dr. Priyanka Patel

At the 13th International Conference on Typhoid and Other Invasive Salmonelloses, Dr. Priyanka Patel of the Malawi Liverpool Wellcome Trust presented her research on the typhoid conjugate vaccine in Malawi. Here she shares updates from her presentation.

Why is the typhoid conjugate vaccine a game-changer in efforts to protect against typhoid?

The Phase 3 typhoid conjugate vaccine (TCV) trial in Malawi has demonstrated that a single dose offers protection against typhoid for at least 4 years. Antimicrobial resistance (AMR) is a major global health challenge and with the emergence of XDR typhoid (resistant to all known antibiotic treatments) in Asia, our only tool for combating new resistant strains is through the typhoid conjugate vaccine. It not only prevents typhoid but will also aid in combating the spread of AMR. The results of the trial in Malawi have not only informed policy locally but will also aid in transforming the landscape of typhoid in many endemic countries. (Editor’s Note: A final analysis of this study showing the effectiveness of single-dose TCV vaccines in Malawi was published in The Lancet on January 25, 2024.)

What are some of the barriers to widespread adoption of TCV?

Resistance to vaccine uptake due to misconceptions. There have been many vaccine campaigns in Malawi preceding the typhoid conjugate vaccine campaign which included COVID, MR, cholera and polio. There was community as well as vaccinator fatigue as a result of multiple vaccine campaigns. Also, infrastructural damage caused by Cyclone Freddy in Malawi made it very challenging to reach populations as roads were inaccessible.

What are some of the questions that you address in your ongoing research on TCV?

The WHO identifies the need for a TCV booster as a knowledge gap. We have just concluded a sub-study where children received a booster dose of the typhoid conjugate vaccine. We hope that the results of this study will be able to fill in the knowledge gap for the need for booster dose and aid stakeholders and policymakers to inform decisions in the near future.

We are also currently doing a Phase 4 study measuring the effectiveness and impact of the TCV post-TCV introduction in Malawi.

What is on the horizon in terms of preventing typhoid: more access to TCV? Additional vaccines?

There was a national TCV campaign led by the Malawi Ministry of Health in May 2023. The TCV is now part of the country’s routine Expanded Programme of Immunization and is being administered to children together with the measles-rubella vaccine. We hope that this will aid in reducing the burden of typhoid in Malawi.


Read about the conference