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Prior infected given first Covid-19 vaccine dose well protected; divert their second dose: AIG researchers

The findings are based on the assessment of 280 healthcare workers
Last Updated 11 June 2021, 14:52 IST

Previously infected individuals given a single dose of Covid-19 vaccine have mounted up to 10 times more immune response and memory cell responses lasting up to one year, compared to the unexposed who also received the first jab, a study conducted at the city-based Asian Institute of Gastroenterology has shown.

The findings are based on the assessment of 280 healthcare workers of the ICMR recognized Covid-19 care facility, who were vaccinated with Covishield between January-February. 131 of them were RTPCR test positive cases earlier. The work has recently appeared in the International Journal of Infectious Diseases (IJID).

Citing the results, AIG researchers including the hospital chairman Dr Nageshwar Reddy are advocating a strategy where the second dose of the previously infected cases is instead diverted to vaccinate and offer protection to a larger, unexposed population.

The recommendation comes at a time when the nation is still facing a severe crunch in vaccine supply.

Read more: Covid-19 crisis: How the vaccination drive is progressing in Karnataka districts

“We found that the amount of antibodies produced in the previously infected after the first dose is 10 times more than the unexposed persons. Their memory cell response to SARS-CoV-2 could last up to 12 months, compared to three months among the latter,” Dr Reddy told DH.

“While individuals with no prior Covid-19 exposure would be required to take the second dose; the second dose in the case of the previously infected could be used as a booster shot next year,” Dr Reddy says.

Though it is known that individuals with Covid-19 infection demonstrate immune memory to SARS-CoV-2 infection and higher antibody response to a single dose of mRNA vaccine than non-exposed individuals, AIG researchers said their study was to measure the efficacy to generate immunological memory among the previously infected after a single dose of vector-based vaccine.

“Our study reports higher memory T and B-cell responses in addition to higher antibody response with a single dose of Covishiled given at 3–6 months after recovery,” said Dr Mitnala Sasikala, corresponding author of the study.

“We are now assessing the immunity and memory cell responses with Covaxin and Sputnik V vaccines too,” Dr Reddy said

Of the 280 individuals enrolled in the study, 131 were RTPCR positive with mild to moderate disease, and 50 had required hospital admission. All the infected 131 (46.78%) were sero-positive, and the remaining 149 (53.22%) were sero-negative before the first vaccination dose. All the participants were given Covishield (AstraZeneca vaccine, manufactured by the Serum Institute of India) in two doses, 28 days apart.

“Baseline neutralizing antibodies were significantly higher in previously infected individuals compared with the no prior exposure group. All the sero-positive and 94.6% of sero-negative participants developed neutralizing antibodies by day 28 after the first dose. The previously infected group mounted greater antibody response and memory CD4+ T-cell responses elicited were also significantly higher compared with the no prior exposure group,” said the IJID article titled “Immunological memory and neutralizing activity to a single dose of Covid-19 vaccine in previously infected individuals.”

“Our results demonstrate evidence to support a single-dose vaccination strategy for previously infected individuals to increase coverage and protect a larger number of populations,” Dr Mitnala said. “Longitudinal follow-up studies are necessary to assess the longevity of protective memory to determine the timing of the second dose.”

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(Published 11 June 2021, 14:52 IST)

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