NEW DELHI : The effect of covid-19 vaccine Covishield starts waning after six months of vaccination, a research study found, making a case for booster doses to protect from the viral pandemic.
According to the study conducted by Pune’s ICMR-National Institute of Virology (NIV), neutralizing antibodies, which are generated by the body after infection or vaccination and guard against future infection, become less effective after this period.
The study, funded by the Indian Council of Medical Research (ICMR), was conducted in February and March, and published in the latest issue of Journal of Infection.
The NIV researchers collected blood samples from three groups of individuals. The first group of 24 so-called ‘covid-19 naïve’ individuals had neither contracted the virus before nor been vaccinated against it; the second group of 17 had recovered from covid-19 and had then received two doses of Covishield; and the third group of 46 had contracted covid-19 after receiving two doses of Covishield, in what is called breakthrough infections. “The neutralizing antibodies (NAb) titres were lowest for Omicron with serum samples of covid-19 naïve vaccinated individuals than the recovered cases and breakthrough cases.