New Delhi: SARS-CoV-2 (Delta variant) had affected more than 200 million people causing more than 5 million deaths worldwide as per the WHO statistics. The rise in mutant variants of the SARS-CoV-2 virus led to concerns regarding vaccine effectiveness with the Delta (B.1.617.2) variant being a predominant strain in India.
The vaccination programme in India is driven largely by the Covishield vaccine (ChAdOx1 nCoV-19). A multi-institutional team of Indian researchers led by the Translational Health Science and Technology Institute (THSTI) evaluated the real-world vaccine effectiveness of Covishield during the SARS-CoV-2 infection surge between April and May 2021, in India.
They also assessed neutralising activity and cellular immune responses against the Variants in healthy vaccinated persons to understand the mechanisms of protection.
Read: Covishield may offer over 90% protection against death from Delta variant: Study
According to the journal “The Lancet Infectious Diseases” which included a comparison between 2379 cases of confirmed SARS-CoV-2 infection and 1981 controls, the vaccine effectiveness against SARS-CoV-2 infection in fully vaccinated individuals was found to be 63%, while the vaccine effectiveness against the moderate-to-severe disease was much higher at 81%.
Significantly, scientists have also observed that the Spike-specific T-cell responses were conserved against both the delta variant and wild-type SARS-CoV-2. Such cellular immune protection might compensate for waning humoral immunity against the virus variants and prevent moderate-to-severe disease and the need for hospitalisation.
