The durability of immunity after the COVID-19 infection persists for at least 9 months as per the evidence-based studies from different countries globally, said Dr. Balram Bhargava, Director General, Indian Council of Medical Research (ICMR) on Thursday.
"The durability of immunity after the Covid infection persists for at least 9 months. If you get an infection for 9 months you are generally protected that's evidence-based studies from different countries globally," said DG, ICMR while briefing media persons.
"Immunological memory for SARS-CoV-2 lasts for >=8 months after natural infection this is from the USA, then Persistence of antibody and cellular immune responses >= 9 months after infection in China ."
"In another study done in the USA published in Nature 2021, most patients had detectable SARS-CoV-2 antibody responses persisting for more than 13 months after infection, and Systematic review of 10 studies from Israel, England, Denmark, USA, Austria, and Italy showed more than 90 per cent of the reduction in reinfection for up 10 months," he explained
According to the three evidence-based studies on immunity conducted in India, Dr. Bhargava said, " the Study conducted in Pune, Chennai, and Mumbai on 284 patients, 755 patients, and 244 healthcare workers respectively showed immunity up to 8, 6 and 7 months."
"The immunity provided by a natural infection lasting up to 8 to 13 months, so we have taken a conservative of nine months, then vaccination can provide immunity and majority of Indians have received either of the two vaccines. Some had the prior infection before vaccination and some had prior asymptomatic infection," he said
On vaccination immunity, he explained, "In essence, many individuals had multiple exposures to SARSCoV2 antigen, whether through the vaccines or through infections or through contact and the durability of this immunity also persists for up to or more than 9 months".
"Recovered and vaccinated (Hybrid Immunity) mounts a slightly stronger response. Robust antibody titers after the second dose for more than 6 months that is published in the very important journal called Nature," he added.
After explaining the studies done in other countries, he also explained the studies conducted in India on immunity and vaccination.
"The study from Kolkata says the duration of persistence of Cell-Mediated Immunity is 10 months in vaccinated individuals in both Covishield and Covaxin. All vaccines are primarily disease modified, they don't prevent infection so they are not infection preventing," Dr. Bhargava said.
( With inputs from ANI )
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