Indigenous cholera vaccine close to trial

Drug trial

They have also proposed to map eight risk zones to accurately monitor prevalence of cholera, which would prepare the vaccine’s introduction and would save thousands falling victims to the disease.

“We are planning for the phase-II clinical trial on 500 volunteers. The field is being prepared. We hope to complete the trial in the next six months,” GB Nair, director of National Institute of Cholera and Enetric Diseases here told Deccan Herald.

A team made of researchers from NICED, Indian Institute of Chemical Biology, Kolkata and Institute of Microbial Technology, Chandigarh developed the oral cholera vaccine using a live-but-weakened strain of cholera-causing bug, Vibrio cholerae.

The first version of the indigenous vaccine was found safe and effective in two rounds of human trial between 2000 and 2005. But since it contained an “antibiotic-resistance gene” as the marker, scientists were asked to modify the vaccine. The new version, which will be tested in Kolkata, is from the controversial marker.

The indigenous vaccine has two distinct advantages over two other products currently available in the market. Swedish vaccine Duckoral is expensive and used primarily as the vaccine for travellers visiting cholera-endemic areas, while Shanchol – developed by Seoul based International Vaccine Institute and manufactured by Shantha Biotechnics in Hyderabad – is a two-dose vaccine making it difficult for health workers to ensure full vaccination in the public health system.

If the recipient does not return after two weeks for the second dose, the Rs 400 vaccine (Shanchol) won’t protect much. The indigenous vaccine, on the other hand, is a single-dose vaccine and easy-to-use in a public health care delivery system. However, the first generation home-made vaccine was found only 53 per cent effective as against 70 per cent efficacy of Shanchol whereas the efficacy of the second generation vaccine would be known only after the phase-II trial is completed.

The World Health Organisation advocates use of cholera vaccine in specific risk areas rather than mass vaccination to prevent outbreaks and disease spreading. The World Health Organisation advocates use of cholera vaccine in specific risk areas rather than mass vaccination to prevent outbreaks and disease spreading.

Diarrhoeal diseases kill an estimated 400,000 children and adults in India every year, a sizeable chunk of which is due to cholera. 

“Diarrhoeal deaths account for 78 per cent deaths in south east Asia. We need some intervention and vaccine is one of them,” Nair said. In the absence of a nationwide cholera surveillance system, the study  will help locate the areas, where the indigenous vaccine could be used when it is ready. map the target areas, NICED has proposed a Rs 12 crore multi-centric study to identify cholera-endemic pockets in Mumbai, Tamil Nadu, Kerala, Chandigarh, Kolkata, Bhubaneswar and Jabalpur, said T Ramamurthy, a NICED scientist.