Single-dose cholera vaccine could help to control outbreaks

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New research has suggested that a single, high-dose cholera vaccine, termed CVD 103-HgR and developed by the University of Maryland (MD, USA), could provide faster protection, helping to control outbreaks more rapidly.

Each year there are over 3 million cases of cholera worldwide, with the WHO estimating over a million cases in Yemen in 2017 alone. While the standard regimen uses a non-living oral cholera vaccine comprising of two doses over a 2-week period, this Phase II trial now suggests that giving a stronger single-dose of live oral vaccine could aid in controlling outbreaks more quickly.

The study, published in Clinical and Vaccine Immunology, enrolled 150 individuals in Mali aged 18–45 years old. The participants were randomized to receive the standard regimen, two doses of Shanchol, or a single, high-dose injection of CVD 103-HgR and a placebo injection, in order to maintain blinding.

The team assessed the antibody-generating ability of both vaccines, a measure known to correlate with protection. They discovered that the rate of seroconversion following the first dose of Shanchol was significantly lower than that following the high dose of CVD 103-HgR. This suggests the high-dose vaccine may be a more effective method to rapidly protect individuals in large outbreaks.

Senior Author, Myron M. Levine (University of Maryland) commented: “Immunization with a single-dose cholera vaccine that could rapidly protect people in low-income countries who have not previously been exposed to cholera would be a significant asset in helping control outbreaks and lower mortality rates. Given the highly encouraging results, we envision that as a matter of priority high-dose CVD 103-HgR will now be evaluated more completely in low income countries menaced by cholera.”

The team recommends an accelerated evaluation of the vaccine in developing countries in order to assess its efficacy and practicality in field situations. They hope to now study whether CVD 103-HgR is suitable for early intervention during outbreaks, or as a pre-emptive vaccine to decrease the burden of seasonal cholera. In addition, the researchers aim to assess the vaccine in young children, who are less well-protected by the current vaccine regimen when compared with adults.

Nima Farzan, Chief Executive Officer and President of PaxVax, who licensed and manufactured the novel vaccine, concluded: “The data published in Clinical and Vaccine Immunology is a first step in demonstrating the potential utility of a new formulation of Vaxchora (CVD 103-HgR) at a higher dose in endemic settings.”

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Sources: Sow SO, Tapia MD, Chen WH et al. Randomized, Placebo-Controlled, Double-Blind Phase 2 Trial Comparing the Reactogenicity and Immunogenicity of a Single Standard Dose to Those of a High Dose of CVD 103-HgR Live Attenuated Oral Cholera Vaccine, with Shanchol Inactivated Oral Vaccine as an Open-Label Immunologic Comparator. Clin. Vacc. Immunol. 24(12) e00265–17 (2017); www.medschool.umaryland.edu/news/2017/High-Dose-Cholera-Vaccine-Developed-by-UMSOM-Scientists-Shows-Promise-for-Controlling-Outbreaks.html

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