WHO Grants Prequalification to Typhoid Vaccine Developed by SK bioscience, International Vaccine Institute

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The World Health Organization (WHO) has granted SK bioscience with prequalification (PQ) certification for its typhoid conjugate vaccine (TCV), SKYTyphoid (NBP618). The vaccine—developed through a collaboration between SK bioscience and the International Vaccine Institute (IVI) with support from the Bill & Melinda Gates Foundation—marks the fourth WHO PQ granted to SK bioscience, following PQs for vaccines that protect against influenza and varicella.¹

Two TCVs have previously received WHO PQ since December 2017, which have been introduced into childhood immunization programs in typhoid endemic countries. The organization estimated that 11 million to 20 million individuals will become infected with typhoid with 120,000 to 160,000 annual deaths.¹

"Typhoid fever is more prevalent in warmer temperatures, and climate change and the worrying rise of antimicrobial resistance are only adding to the threat of the disease,” said Jerome Kim, MD, IVI director general, in a press release. “Vaccination is critical to effective prevention and control of the disease. In collaboration with SK bioscience and other partners, IVI will continue endeavors to make this vaccine accessible to people who need it the most."¹

Although typhoid can be treated with antibiotics, resistance to treatment has become common increasing the likelihood of costlier treatments in the most affected regions. The infection can still be transmissible even after symptoms have dispelled.²

SKYTyphoid was developed via the purified Vi polysaccharide-diphtheria toxoid conjugate method. This process “conjugates a polysaccharide of typhoid bacteria, serving as an antigen, to a diphtheria toxin protein (diphtheria toxoid), that acts as a carrier.”¹

According to SK bioscience, the conjugate technology allows SKYTyphoid to be safely administered to individuals as young as 6 months of age to 2 years of age. The company stated that it expects the single-dose vaccine to provide comparable immunogenicity and long-term protection compared with current oral live or polysaccharide typhoid vaccines.

The efficacy of SKYTyphoid was demonstrated in a trial that enrolled 2,160 individuals in Nepal aged 6 months to 45 years. The vaccine showed a positive immunogenicity and safety profile compared to current polysaccharide-protein conjugate typhoid vaccines with WHO PQ certification. These findings were observed across all age groups.

“In conclusion, our findings show that conjugated Vi-DT vaccine is safe and immunogenic in infants and toddlers,” the study authors wrote. “Furthermore, we found the persistence of anti-Vi seroconversion at 28 weeks in the single dose group, and follow-up is ongoing for 2 years between single-dose and two-dose regimens of Vi-DT vaccines. A booster dose at two years is planned for the single-dose group. Large-scale phase 3 studies with the single-dose of Vi-DT have started with the objective of achieving WHO prequalification and improving the supply of TCV, an important vaccine for global health.”³

Following the WHO PQ, SK bioscience stated it will focus on global markets with the vaccine, targeting public procurement markets that include typhoid-endemic regions with high demands.

"We are pleased that our global collaboration to address the global vaccine supply imbalance and improve public health has been recognized by the WHO PQ certification," said SK bioscience CEO Jaeyong Ahn, in a press release. "We will make every effort to rapidly supply SKYTyphoid by obtaining approvals in countries."¹

References

1. SK bioscience Receives WHO Prequalification for Typhoid Conjugate Vaccine. SK bioscience. News release. February 23, 2024. Accessed February 23, 2024. https://prnmedia.prnewswire.com/news-releases/sk-bioscience-receives-who-prequalification-for-typhoid-conjugate-vaccine-302069852.html

2. World Health Organization. Typhoid. Webpage. Updated March 30, 2023. Accessed February 23, 2024. https://www.who.int/news-room/fact-sheets/detail/typhoid#:~:text=Overview,and%20spread%20into%20the%20bloodstream.

3. Capeding MR, et al. Immune persistence and response to booster dose of Vi-DT vaccine at 27.5 months post-first dose. NPJ Vaccines. 2022 Jan 27;7(1):12. doi: 10.1038/s41541-022-00434-8. PMID: 35087084; PMCID: PMC8795159.