Preliminary study shows Covishield protects against double mutant variant

Preliminary studies carried out at CCMB show that people who have been vaccinated with Covishield have protection against the double mutant variant (B.1.617) first found in India. Protection against the variant was also seen in people who have been previously infected with SARS-CoV-2 virus.

Preliminary studies show that people who have been vaccinated with Covishield have protection against the double mutant variant (B.1.617) first found in India. Studies by researchers at the Hyderabad-based Centre for Cellular and Molecular Biology (CCMB), a CSIR lab, found that protection against the double mutant variant was also seen both when convalescent plasma from people who have been infected and have already recovered was tested in the lab.

“Both Covishield vaccinated sera and convalescent sera were found to offer protection against the double mutant variant (B.1.617),” says Dr. Rakesh Mishra, Director of CCMB. “This is only a preliminary study involving four-five people for each group and was carried out among young people who have recovered from prior infection and another group of people who have received Covishield vaccine.”

Dr. Mishra says that in about 10 days, studies involving more people from both groups — who have recovered and who have been vaccinated ­— will be done. Also, the study will involve older people to understand the level of protection conferred by previous infection and by Covishield vaccine.

“The study, though preliminary, does show that vaccination with Covishield offers protection against the double mutant variant. So people should go ahead and get vaccinated quickly,” says Dr. Mishra. “The preliminary study also suggests that convalescent plasma may offer protection against reinfection with the double mutant variant. Studies using plasma from more recovered and vaccinated people of different age groups are needed for confirmation.” The Institute is carrying out similar studies using plasma from people vaccinated with Covaxin.

Combined effect of two mutations not known

The B.1.617 variant has two mutations — E484Q and L425R — of concern.

According to Dr. Vinod Scaria, a senior scientist at the Delhi-based Institute of Genomics and Integrative Biology (IGIB), a CSIR lab, the two mutations have individually been found to make the virus more infectious and evade antibodies. But the combined effect of these two mutations when found together has not been determined.

“The two mutations when found together could alter the structure of the spike protein in unanticipated ways. Therefore, we cannot predict with utmost accuracy whether the two mutations when present together will further increase or reduce the infectivity and ability to evade specific antibodies. The CCMB study shows that serum from people vaccinated with Covishield could inhibit the B.1.617 variant of the virus. More detailed studies involving larger number of people is the way forward,” Dr. Scaria says.

Protection in previously infected, Covishield vaccinated people 

Studies found that in the lab, the convalescent plasma from recovered people was able to neutralise the double mutant variant almost completely even when the plasma was diluted 20-fold. The relative viral load seen when the plasma was diluted 40- and 80-fold was about 2-3%. The relative viral load reached nearly 65% only when the plasma was diluted 320-fold, showing the effectiveness of convalescent plasma in neutralising the double mutant variant.

Neutralisation studies carried out using plasma from Covishield-vaccinated people showed that the level of protection against the double mutant variant was far superior than convalescent plasma.

Even when the plasma from Covishield vaccinated people was diluted 80-fold, the relative viral load was almost nil. In simple terms this means that even 80-fold diluted plasma is effective against the double mutant variant. It was only when the plasma of vaccinated people was diluted 320-fold did the relative viral load increase and reach nearly 55%.

In Maharashtra, the double mutant variant (B.1.617) was found in more than 60% of samples taken for genome sequencing.

Published in The Hindu on April 23, 2021