Safety of An Oral O1 / O139 Cholera Vaccine (Enteric Capsules)

Cholera is an acute enteric infectious disease caused by the bacterium Vibrio cholera, leading to watery diarrhea and loss of fluids from the small intestines. The disease can quickly lead to severe dehydration and death without proper and timely management. The World Health Organization (WHO) estimates that up to 4.3 million cholera cases annually with more than 100,000 of them result in death in worldwide. The high morbidity and consequent mortality caused by cholera is attributable to several factors, including lack of access to safe drinking water, poor sanitation and poor hygiene practices and transmitted via the fecal-oral route by ingesting food or water contaminated with the bacterium. Cholera is a significant public health issue in many developing countries in Africa, Southeast Asia, the Caribbean, and South America, and is rare in industrial countries with most cases occurring in travelers who have visited cholera-affected areas.

Cholera is mainly caused by the O1 or O139 serogroups of V. cholerae among the more than 200 V. cholerae serogroups, O1 strains are divided into two biotypes: Classical and El Tor. Each biotype can be further divided into 3 serotypes: Inaba, Ogawa, Hikojima. V. cholerae O1 has been shown to be responsible for the first six cholera pandemics. In 1992, a new V. cholerae serogroup O139 emerged and it has caused epidemics that spanned most of Asia. This strain was a genetic derivative of El Tor biotype in which the O1 biosynthetic genes were replaced by the O139 biosynthetic genes. Both V. cholerae O1 and O139 can produce an enterotoxin, which causes serious diarrhea, causing dehydration, and can lead to death in a few days.

Vaccination has been shown to be a cost-effective, more immediate option for cholera control and prevention. Injectable vaccine is not recommended by the World Health Organization (WHO) mainly because of its limited efficacy less than 50% and short duration of protection almost no more than six months. Enteric vaccination has already been regarded as the most effective approach to control such illnesses as well as to prevent cholera in endemic countries. The inactivated whole-cell, bivalent O1 and O139 cholera vaccine have provided evidence of substantial protective efficacy up to 60% at least 3-5 years. In 2011 the first low-cost oral cholera vaccine for international use was given prequalification by the World Health Organization (WHO). With the goal of making an ideal low-cost OCV that could be used in cholera-endemic countries, a phase I trial was conducted to estimate safety of the oral O1 / O139 cholera vaccine (enteric capsules), in order to fulfill the requirements of WHO. On the other hand, China is a non-endemic country of cholera, it will also can provided a safe and convenient vaccine for the travellers who visited cholera-affected areas.