First Conjugate Vaccine for Typhoid Prequalified by WHO

The World Health Organization (WHO) announced that it prequalified the first conjugate vaccine for typhoid, Bharat Biotech’s Typbar-TCV, at the end of December 2017.

Typhoid is a water-borne infection caused by the bacterium Salmonella enterica serotype typhi. It is spread through contaminated food and water. Symptoms of the infection a “high fever [103° to 104° F (39° to 40° C], weakness, stomach pains, headache, or loss of appetite. In some cases, patients have a rash of flat, rose-colored spots,” according to the Centers for Disease Control and Prevention (CDC). The estimated global burden of the disease ranges from 11 to 20 million cases and contributes to about 128,000 to 161,000 deaths each year. Individuals living in low- and middle-income countries bear the greatest burden. The poorest communities and vulnerable groups such as children are most at-risk.

The CDC states that “without therapy, the illness may last for 3 to 4 weeks and death rates range between 12% and 30%.” Antibiotics available to treat the infection include fluoroquinolones (for susceptible infections), ceftriaxone, and azithromycin. However, an increase in antibiotic-resistant strains of the infection has spurred a call for a better vaccine, particularly one that can be given to one of the most vulnerable populations, children. The Typbar-TCV may be that vaccine.

According to the WHO, “Typhoid conjugate vaccines (TCVs) are innovative products that have longer-lasting immunity than older vaccines, require fewer doses, and can be given to young children through routine childhood immunization programs. In October 2017, the Strategic Advisory Group of Experts (SAGE) on immunization, which advises WHO, recommended TCV for routine use in children over 6 months of age in typhoid endemic countries. SAGE also called for the introduction of TCV to be prioritized for countries with the highest burden of typhoid disease or of antibiotic resistance to Salmonella typhi.” The officials hope that the use of the vaccine will halt the inappropriate use of antibiotics for possible cases of infection and therefore slow the rate of antibiotic resistance.

This prequalification from WHO is an important step to getting the vaccine made available in low-income countries. According to WHO, “WHO prequalification helps to ensure that vaccines used in immunization programs are safe, effective, and appropriate for countries’ needs. WHO’s prequalification procedure consists of a transparent, scientifically sound assessment that includes reviewing the evidence, testing the consistency of each lot of manufactured vaccine, and visiting the manufacturing site.”

Although typhoid is exceedingly rare in the United States, the increase in globalization, flooding brought on by extreme weather conditions, and the rise in antibiotic resistance could set the country up for an outbreak. There are currently 2 vaccines against typhoid fever available in the United States: Ty21a (Vivotif Berna, Swiss Serum and Vaccine Institute), and ViCPS (Typhim Vi, Pasteur Merieux). Individuals need to receive the vaccine at least 1 to 2 weeks prior to exposure, however, so that the vaccine has time to take effect, according to the CDC.