Covishield had 63% effectiveness against Delta variant in second wave

Offered 85% protection against moderate or severe disease, says Faridabad study

Two shots of Covishield gave 63% protection against symptomatic SARS-CoV2 infection and 85% protection against moderate or severe disease, say the results of a study conducted in Faridabad, Haryana to assess the effectiveness of vaccine. The study notably was conducted during the second wave when the Delta variant was dominant.

While several studies — as did the latest study — have shown that vaccination elicited fewer neutralising antibodies against the Delta variant compared to the wild type variant, the Haryana study found that there wasn't any significant reduction in cellular immunity.

This category of immunity, also called T cell immunity, results from the body learning to destroy the coronavirus after having being taught to do so from either a vaccination or a previous infection and is considered more long lasting than the protection conferred from neutralising antibodies which are produced within weeks of an inoculation or infection.