Brazil Dengue Vaccine Deaths Trigger Safety Concerns
Why in the News ?
The suspension of Brazil’s Butantan-DV dengue vaccine after reports of severe adverse events and two deaths has raised concerns about the safety of India’s upcoming DengiAll vaccine, as both are based on similar vaccine technology. This development highlights the importance of the precautionary principle in vaccine deployment.
Concerns Over India’s Upcoming DengiAll Vaccine :
● Brazil temporarily suspended the Butantan-DV dengue vaccine after 42 severe adverse events, including two deaths and one intensive-care case among nearly 5 lakh vaccinated individuals.
● Scientists have highlighted similarities between Butantan-DV and India’s DengiAll, both developed using technology licensed from the U.S. National Institutes of Health (NIH).
● Both vaccines are tetravalent, containing weakened forms of all four dengue virus serotypes (DENV-1, DENV-2, DENV-3, and DENV-4).
● Experts have called for a detailed ex post facto investigation into whether the severe cases were linked to Antibody-Dependent Enhancement (ADE), a phenomenon that can worsen dengue infections.
● Concerns have emerged regarding whether DengiAll could face similar safety challenges once introduced in India.
Scientific Challenges and Need for Vigilance
● Dengue infection generates type-specific antibodies and cross-reactive antibodies against different virus serotypes.
● When cross-reactive antibody levels decline, they may facilitate ADE, leading to severe dengue complications instead of protection.
● Previous experience with Dengvaxia, the world’s first dengue vaccine, showed that incomplete immunity against all serotypes could increase severe disease risk.
● Questions remain about Butantan-DV’s effectiveness against DENV-3 and DENV-4, as these serotypes were not sufficiently prevalent during Phase-III trials in Brazil.
● Experts recommend extensive testing of DengiAll to ensure balanced immunity against all four serotypes before regulatory approval.
| About Dengue and Vaccine Development : ● Dengue is a mosquito-borne viral disease transmitted by the Aedes aegypti mosquito. ● The disease is caused by four distinct serotypes: DENV-1, DENV-2, DENV-3, and DENV-4. ● Infection with one serotype provides lifelong immunity against that serotype but only temporary protection against others. ● Antibody-Dependent Enhancement (ADE) occurs when non-neutralizing antibodies enhance viral entry into cells, increasing disease severity. ● India’s DengiAll vaccine is undergoing Phase-III clinical trials involving over 10,000 volunteers, with participants being monitored for two years before potential regulatory approval. |