If findings of researchers at the Asian Institute of Gastroenterology are any indication, one dose of Covid-19 vaccine would do for those who were already infected once. The findings of the study would help in fine-tuning the vaccine administration strategy in the country.

The AIG has roped in 280 health workers and were administered Covishield in two doses with a gap of 28 days. Of the 280 individuals enrolled in the study, 131 were RT-PCR positive with mild to moderate disease, and 50 required hospital admission.

The study, published in the International Journal of Infectious Diseases, found that previously infected individuals showed higher neutralising antibody response. It found a higher memory cell response in such individuals.

“Single dose vaccination in previously exposed individuals is an efficient strategy,” an AIG spokesperson said, quoting the study.

He said the findings would help in reaching out to a much larger population, considering the shortages in vaccine supplies.

“Our study reports higher memory T and B-cell responses in addition to higher antibody response with a single dose of Covishield given at 3–6 months after recovery from the Covid-19 infection,” the study said.

Adaptive immune memory

They can trigger a memory recall response on a subsequent encounter with antigen as they have developed adaptive immune memory.

If a single dose could induce adequate immunological memory in previously infected individuals in addition to a higher neutralizing activity, the second dose could be diverted to vaccinate and protect a larger population.

Those who were not exposed to the infection would require to take the second dose. The AIG, however, said that follow-up studies need to be taken up to ascertain the longevity of protective memory and determine the exact timing of the second dose.

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