On guard: on India and the Qdenga dengue vaccine

The CDSCO’s approval of the Qdenga dengue vaccine — the first in India’s history — follows the vaccine’s licensing in over 40 countries and a WHO prequalification, and some of the country’s worst dengue years vis-à-vis the disease’s burden, although that is evidence of better surveillance as well. The Aedes mosquitoes that spread the disease are expanding into semi-urban and rural districts, where conventional vector control is harder to sustain. The time to develop the vaccine itself is understandable. The four antigenically distinct dengue serotypes and the possibility of a ‘second infection’ by a different serotype producing more severe disease through antibody-dependent enhancement mean that an effective shot has to induce strong immunity against all four at once. This constraint nearly derailed the first licensed dengue vaccine, Dengvaxia, and the controversy in the Philippines in 2017 prompted greater regulatory caution. The design of Qdenga, by Japan-based Takeda , differs from that of Dengvaxia and, unlike the latter, can be administered without screening for a prior dengue infection.