Durability of immunity post Covid vaccination persists for 9 months or more: Govt

The durability of immunity post Covid-19 vaccination persists for nine months or more and a precautionary dose of vaccine which will be administered to healthcare and frontline workers and citizens above 60 years with comorbidities is to mitigate the severity of infection, hospitalisation and death, the government said on Thursday.

ICMR Director General Dr Balram Bhargava said the virus SARS-CoV-2 infects an individual in natural settings and elicits antibody mediated, cell mediated immunity and immunological memory.

He said hybrid immunity, which is developed as a result of vaccination and natural infection, mounts a stronger response and robust antibody titres after the second dose.

Also Read | J&J’s booster provides strong protection against severe disease from Omicron, says Study

Measuring antibody titre only, does not capture the entire protection, he said.

"The durability of immunity post-infection persists for about 9 months," Bhargava told a press conference.

He said hybrid immunity, which is developed as a result of vaccination and natural infection, mounts a stronger response and robust antibody titres after the second dose.

"If you have had an infection and vaccination your immune response is more than only infection or vaccine. So the important thing is that vaccination is absolutely essential," he said.

Citing global evidence, Bhargava said immunological memory for SARS CoV2 lasts for more than eight months after natural infection.

"This is from the US published in Science, and there is antibody and cellular response more than nine months after infection from China. Then longitudinal investigations in the US have multiple studies have shown that the antibody responses persists for more than 13 months post infection and the systematic review of 10 studies from Israel, England, Denmark, US, Austria and Italy have that more than 90 per cent reduction in reinfection up to 10 months," Bhargava said.

Also Read | Amid sudden spike in Covid cases, Govt writes to 8 states/UTs for 'immediate action'

"... We like to say that up to nine months and take a slightly conservative estimate of that and that is what is the evidence. From India there are three studies two from ICMR and one from Mumbai, on 284 patients, on 755 patients and 244 that it persists for up to eight months, seven months and six months (respectively) and these are all published data from infection that occurred in 2020, 2021," he said.

Talking about the vaccines that are being used in India, Bhargava said one is the whole virion kill vaccine with an innovative adjuvant that is the Covaxin and the second is a viral vector based subunit vaccine that is Covishield.

"...So despite vaccination having happened we know the seroprevalence that is also to be factored in. And the third point is that the transmission of Omicron is three times or four times more than the Delta variant also. So that will also be exposing people for this. In terms of the precautionary dose, we have to remember one important point and that is the most important point is that all Covid vaccines are primarily disease modifying and they do not prevent infection. So they are not infection prevention," he said.

Also Read | Govt to decide on Covid vaccine to be given as precautionary dose

Bhargava said the precautionary dose is primarily to mitigate the following three things - one, severity of infections two - hospitalisation and death.

"Now this is very important for individuals who are elderly, immune compromised or on chemotherapy, or patients who have chronic obstructive lung disease. So these are patients where a precautionary dose would be useful to prevent serious disease hospitalization and death," he said.

"The important three points that I want to stress on mask use before and after vaccination is must, mass gathering should be avoided before and after vaccination. And earlier and currently circulating strains spread through the same route. They are all spreading through the respiratory tract through the airborne. So we have to remember that whether the virus is mutating it spreads by the same route," he said.

Bhargava said the treatment does not seem to remain change it remains the same. "

Home isolation remains an important parameter and hospitalisation will be limited to those particularly those who are unvaccinated. Those who are unvaccinated will be the ones who will be admitted to hospitals, people who are immunocompromised and chemotherapy will be the ones who will be admitted to hospitals and will require more care," he added.

Check out DH's latest videos: