India's Dengue Vaccine DengiAll Under Scrutiny After Deaths in Brazil

The death of two people in Brazil during its dengue vaccination drive, which led the country to suspend the shot on 8 June 2026, has raised serious questions for India. The reason is that Brazil's vaccine, Butantan-DV, is very similar, if not identical, to India's soon-to-be-launched dengue vaccine, DengiAll. Both were built over several years, both use live but weakened dengue viruses, and both are tetravalent, meaning each is a mixture of four weakened forms of the virus.

The dengue virus comes in four versions, called serotypes DENV-1 to DENV-4, and all four are common in both India and Brazil. Each serotype carries envelope proteins on its outer shell. A vaccine made from weakened virus triggers two kinds of antibodies. Type-specific antibodies, made in small amounts, block only one serotype well. Cross-reactive antibodies, usually made in larger amounts, can recognise all four serotypes. But when the level of these cross-reactive antibodies falls, they no longer block infection and instead make it worse, leading to a severe and sometimes fatal form of dengue. This is called antibody-dependent enhancement, or ADE, and it is the central safety worry for any dengue vaccine.

In Brazil's campaign, 42 vaccine recipients showed serious side effects. Two of them died and one needed intensive care. The symptoms included severe abdominal pain, persistent vomiting and bleeding, which resemble severe dengue itself and which had not appeared during the phase 3 trials. Researchers will need to study whether ADE was the cause, and whether DengiAll could carry the same risk when it is rolled out in India. There is also a known precedent: about a decade ago a different vaccine, Dengvaxia, given to more than eight lakh children in the Philippines, caused severe events three years later because it ended up protecting against only one serotype rather than all four.

A separate landmark study, published in the journal Science Translational Medicine, offers hope for building safer immunity. Following nearly 3,000 children in the Philippines, researchers identified a special group of antibodies, known as envelope dimer epitope or EDE-like antibodies, as the key to broad protection against all four serotypes. These antibodies were found in 82 to 90 percent of children who already had strong immunity from two past infections, but were almost absent in those with only a single past infection. Higher levels of these antibodies were consistently linked to a lower chance of falling ill, of dengue with warning signs, and of needing hospital care.

For India, the picture is one of both caution and direction. DengiAll's phase 3 trial, run by Panacea Biotec with the Indian Council of Medical Research, finished enrolling 10,335 healthy volunteers in January 2026, who will be followed for two years. Experts say India can act early to reduce risk: the maker should test blood samples from vaccinated volunteers for type-specific antibodies against all four serotypes, the drug regulator should confirm this data rules out ADE risk, and a strong long-term safety-monitoring programme should be put in place once the vaccine is launched.