Uncovering Advantages of the New Typhoid Vaccine

A 3-dimensional (3D), computer-generated image of a number of Salmonella serotype Typhi bacteria.
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A 3-dimensional (3D), computer-generated image of a number of Salmonella serotype Typhi bacteria. CDC/James Archer

Yesterday’s announcement that WHO has prequalified the first conjugate vaccine for typhoid offers a major boost to prevention efforts against a disease that causes 11–20 million cases annually and up to 161,000 deaths.

The vaccine—Bharat Biotech’s Typbar-TCV®—offers significant advantages over previous vaccines, including the need for fewer doses and its use in children under the age of 2, says Kathleen M. Neuzil, MD, MPH, director, Center for Vaccine Development at the University of Maryland School of Medicine.

 

Why is WHO’s prequalification of this vaccine important and how will it change the prevention of typhoid?

WHO prequalification is a critical step in expanding access to lifesaving typhoid conjugate vaccines. Prequalification ensures that vaccines provided through the United Nations for use in national immunization services are safe, effective and suitable for the target populations at the recommended immunization schedules, and allows UNICEF, and other United Nations procurement agencies to purchase Typbar-TCV. It also enables eligible countries to apply for funding assistance from Gavi, the Vaccine Alliance (Gavi), which recently approved $85 million to support the introduction of typhoid conjugate vaccines, including Typbar-TCV.

At the October 2017 World Health Organization (WHO) Strategic Advisory Group of Experts (SAGE) on Immunization meeting, SAGE recommended the introduction of typhoid conjugate vaccines in endemic countries to all children over six months of age. The incorporation of Typbar-TCV into routine vaccination schedules is the best way to reach children most at risk for typhoid.

Typhoid vaccines – alongside safe water, sanitation, and hygiene interventions – are a critical component to preventing typhoid and reducing the disease’s burden in high-risk, endemic areas.

How significant is the fact that the vaccine, unlike previous typhoid vaccines, can be given to children under 2?

Compared to the currently available vaccines, TCVs have longer-lasting protection, require fewer doses, and are suitable for children younger than 2 years of age, allowing delivery through routine childhood immunization programs. In addition to the enhanced feasibility of delivering vaccines to children younger than two, the burden of illness in these young children is being increasingly recognized, particularly in Africa. Expanded use of TCVs through routine immunization has the potential to reduce the need for antibiotics, slow further emergence of drug-resistant typhoid strains, and reach the children most at risk for typhoid.

Prequalification is obviously an important step—but financing, production and distribution will no doubt present challenges. How long will it take for Typbar TCV to reach children?

Following SAGE recommendations, Gavi, the Vaccine Alliance (Gavi) approved US $85 million to support the introduction of TCVs in Gavi-eligible countries and will begin accepting applications for support in 2018, with introductions in 2019–2020. Prequalification of a TCV, SAGE recommendations, and Gavi financing are all critical pieces of the puzzle that together will facilitate access to TCVs in low- and middle-income countries.

Many factors affect vaccine uptake at the local level. TyVAC, a consortium led by the University of Maryland School of Medicine Center for Vaccine Development in partnership with the Oxford Vaccine Group and PATH is supporting uptake of typhoid conjugate vaccines through a multidisciplinary approach, including support to individual countries in decision-making and preparation for sustained TCV introduction.

Where will the vaccine be distributed first?

Typbar-TCV is licensed for private use in India and Nepal and registered in Nigeria and Cambodia with 30 additional registrations in progress. The vaccine is not yet included in any countries’ national immunization program. However, working with local and international partners, TyVAC is conducting impact studies in Nepal, Malawi and Bangladesh. The Nepal study began in November 2017, the Malawi study is targeted to being in early 2018, with the start of the Bangladesh trial slated for mid-2018.

Independent of TyVAC, efforts are underway for a pilot introduction in the public sector in Navi Mumbai, India. In addition, [as I said], countries will also be given the opportunity to apply for Gavi support for vaccine introduction in the 2019-2020 time frame.

We will have a better idea by the 3rd quarter of this year which countries will be early introducers of typhoid conjugate vaccine in their national immunization programs.

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