New Delhi: A single-dose of Covaxin provides a similar immunity response in previously Covid-infected people as those without previous history of Covid infection with two doses of vaccine, says Indian Council of Medical Research's latest study.
The ICMR in its recent study has found that the people already infected with Covid-19 while taking a dose of Covaxin have the same or increased antibody response as unaffected people taking two doses of Covaxin.
The pilot study was undertaken to examine SARS-CoV-2 specific antibody responses after day 0 (baseline before vaccination), day 28A2 days post-first dose (month 1) and day 56A2 days post-first dose (month 2) of BBV152 in a group of healthcare professionals as well as frontline workers.
The antibody responses of individuals with confirmed pre-vaccination SARS-CoV-2 infection were compared with those individuals without prior evidence of infection.
The blood specimens were collected from healthcare professionals and frontline workers who received BBV152 vaccine at vaccination centres in Chennai, India, during February to May 2021.
Blood samples were collected before receiving the first dose of BBV152. Prior infection with SARS-CoV-2 was determined by SARS-CoV-2 IgG positivity at baseline. The study was approved by the Ethics Committee of ICMR-NIRT.
Antibody levels were measured at three time points: on the day of vaccination (baseline), at month one following the first dose and at month two following the first dose.
The results were determined via a calibration curve, which is an instrument specifically generated by two-point calibration and a master curve provided via the reagent QR code.
Almost all participants with prior Covid-19 infection except two had detectable antibodies at the time of vaccination. This study offers evidence in support of public health-oriented and immunologically sustained vaccine strategies.
Lokesh Sharma, Scientist and Media Coordinator, ICMR, says, "This is a pilot study. If such findings are confirmed in large population studies, a single dose of BBV152 vaccine may be recommended to previously confirmed Covid patients so that the naA-ve individuals could attain the larger benefit of a limited vaccine supply."
As per a report on nature.com, studies show that people with previous exposure to SARS-CoV-2 tend to mount powerful immune responses to single shots, and gain little added benefit from another injection.
France, Germany and Italy, among other countries, now advise only one dose of vaccine for people with a healthy immune system and a confirmed previous diagnosis. Many scientists who have studied immune responses to vaccination say such policies are a sensible way to make the most of limited supplies in countries that are racing to inoculate their populations.
But scientists still don’t know whether one-jab programmes for the previously infected could leave some individuals with suboptimal protection. Nor is it clear that such programmes would be effective for all types of vaccine.
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