India is unlikely to introduce the world’s only vaccine against dengue this year. Experts and Indian Council of Medical Research and National Institute of Virology have said there is limited data or clinical trials to assess the efficacy of the vaccine.
The licensed vaccine, Dengvaxia, has became available in Mexico, Brazil, the Philippines and El Salvador. “Consultations and discussions are under way but we are unlikely to introduce the vaccine in the country this year,” Dr Soumya Swaminathan, director general of Indian Council of Medical Research (ICMR), told The Indian Express. “Instead we are looking at newer strategies for vector control including wolbachia, which is a natural bacterium present in up to 60 per cent of all species of insects including mosquitoes. It is not usually found in the Aedes aegypti mosquito, the primary species responsible for transmitting dengue, chikungunya and zika.”
The dengue vaccine, produced by Sanofi-Pasteur, has been trialled on around 30,000 people from ten countries. A recent study by Imperial College of London has said the vaccine may worsen subsequent infections if used in areas with low rates of the disease. Many areas in India have a high incidence rate, with 36,110 cases this year (until September 11) and 70 deaths, following last year’s 99,913 cases and 220 deaths.
The Imperial College study suggests that in people who have never been exposed to dengue before, the vaccine primes the immune system so that if they are subsequently infected, the infection is more severe. Asked for her view of the study, which was published in Science, Swaminathan said the success of a routine vaccination against dengue depends on a target group that has experienced prior infections. “At this stage there is limited data or clinical trials to assess the efficacy of the vaccine,” she said.
At Serum Institute, officials said it was important that a first vaccine was in place to fight dengue. They said they were working along with National Institutes of Health for a dengue vaccine and clinical trials are likely to start next year.
Although chikungunya is the predominant worry this year — 14,656 cases until September 11, following 27,553 cases last year — outbreaks happen after a cycle of several years while dengue repeats itself more frequently. The strategy is to control the vector, the ICMR head said.
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“However we do need to work on vaccines and draw from experience of other countries as India really does not have enough data to introduce the vaccine immediately.”
She said discussions are under way on wolbachia and research has shown that when introduced into the Aedes aegypti mosquito, wolbachia can stop these viruses from growing and being transmitted to people. “This discovery has the potential to transform the fight against life-threatening viral diseases,” she said. “We can cultivate these special mosquitoes and set up a large facility to breed them before releasing them into the environment so that they compete with the normal mosquito population and check the dengue virus. Already in Australia this technology has successfully brought down cases of dengue.”
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