A study by Hyderabad’s AIG Hospitals has claimed that a single dose of the Covid-19 vaccine is sufficient for those already infected by the disease before. The hospital said it conducted a study on 260 healthcare workers who got vaccinated between January 16 and February 5 to assess the immunological memory response in all those patients. All patients were given the Oxford-Serum vaccine Covishield.
The study comes at a time when the country is looking at vaccinating all eligible people (above 18 years) by the year end. The vaccine is considered the most effective preventive measure to protect from the Covid-19 pandemic that has become a major threat to public health globally.
The previously infected group (people who got infected with Covid-19) showed a greater antibody response to a single dose of vaccine compared with those who had no prior infection.
It also revealed that Memory T-cell responses elicited by a single dose of vaccine were significantly higher in the previously infected group compared with those who had no prior infection.
It was concluded that higher memory T and B-cell responses in addition to higher antibody response with a single dose of vaccine given at 3-6 months after recovery from Covid-19 may be considered at par with two doses of vaccine for individuals already infected with Covid-19.
“The results show that people who got infected with Covid-19 need not take two doses of vaccine yet with a single dose can develop robust antibody and memory cell response at par with two-doses for those who didn’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 Dr. D Nageshwar Reddy, Chairman, AIG Hospitals, and one of the co-authors in the study.
Dr. Reddy further added that “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.”
Experts question Centre's one-dose Covid vaccination efficacy theory:
“India may soon start in few weeks testing the feasibility of a regimen that mixes two different doses of Covid vaccines to see if it helps boost the immune response to the virus," said Dr N K Arora, chairman of Covid-19 working group under National Technical Advisory Group on Immunisation (NTAGI).
Meanwhile, Banaras Hindu University researchers have claimed a single dose of vaccine is enough for Covid recovered patients. “We studied the effect of the vaccine on Covid recovered and non-infected people. Antibodies in recovered people developed in the first week,” Prof Zoology Dept BHU Gyaneshwer Chaubey said.
“While 90 per cent of non-infected people developed antibodies after 3-4 weeks, recovered people developed antibodies after the first dose. By giving a single dose to recovered people, we can overcome vaccine shortage. We've also written a letter to PM in this regard,” the professor said.
C S Pramesh, Director, Tata Memorial Hospital, said there is no data to suggest that one dose of Covishield is good enough to protect from Covid-19.
What did PHE say?
According to a new Public Health England (PHE) study released earlier this week, those given a first dose of either of the two vaccines currently being administered by the National Health Service (NHS) in the UK and who became infected with Covid-19 – three weeks later were between 38 and 49 per cent less likely to pass the virus on than unvaccinated people.
The PHE also found that protection against Covid-19 was seen from about 14 days after vaccination, with similar levels of protection regardless of the age of cases or contacts.
“A new study shows one dose of the vaccine can cut the risk of household transmission by up to 50 per cent. This is further evidence that the vaccine protects you and those around you. When you get the call, get the jab,” said UK Health Secretary Matt Hancock.
The study, which is yet to be fully peer-reviewed, included more than 57,000 contacts from 24,000 households in which there was a lab-confirmed coronavirus case that had received a vaccination, compared with nearly 1 million contacts of unvaccinated cases.