The three vaccines India is using currently – Covaxin, Covishield and Sputnik V – are all being administered in two doses to uninfected people. But is a single dose a better option?
According to a recent study, a single dose of Covishield given to those who had recovered from coronavirus infection showed they had a stronger immunity to the deadly virus compared to those with no prior exposure.
The research, carried out by Asian Institute of Gastroenterology (AIG) Hospital, Hyderabad, was conducted on 260 healthcare workers who were all administered Covishield between January 16 and February 5.
One group comprised people who had tested RT-PCR positive and recovered, while the second group had those who were RT-PCR negative and thus categorised as people with no prior exposure.
The first significant observation that emerged from the study was that the previously COVID-infected group showed a greater antibody response to a single dose of vaccine compared with those who had no prior infection.
Secondly, Memory T-cell responses elicited by a single dose were much higher in previously-infected group.
The inference was that higher memory T and B-cell responses, in addition to higher antibody response, with one vaccine dose given 3-6 months post recovery from COVID-19 may be considered on a par with two doses of vaccine for people who haven’t been infected with the coronavirus.
“The results show that people who got infected with COVID-19 need not take two doses of vaccine and with a single dose can develop robust antibody and memory cell response on a par with two doses for those who haven’t get the infection. This will significantly help at a time when there’s a shortage of vaccines in the country and more people can be covered using the saved doses,” said AIG Hospital chairman Dr D Nageshwar Reddy, one of the co-authors of the study.
“Once we attain the requisite number of people vaccinated for achieving herd immunity, these patients who got infected and received only one dose can take the second dose of the vaccine. At this point, all our strategies should be directed at the widespread distribution of available vaccines and to include the maximum number of people at least with a single dose,” Dr Reddy added.