Lucknow, Jun 10 (IANS): An antibody test, done on 989 KGMU healthcare workers and about 500 plasma donors by the King George's Medical University (KGMU), has found that antibodies formed after vaccination were stronger and lasted longer, whereas those generated after infection fizzled out in less than four months.

The study further found that the desirable herd immunity which can break the chain of virus, can only be achieved by mass vaccination and not through natural course of transmission of infection.

In the two-part study, in which the 989 healthcare workers included class four employees, junior doctors, staff and senior faculty members, 869 (88 per cent) had antibodies.

Of 869, about 73 per cent had completed a two-dose vaccination course and 13 per cent had taken one dose.

The remaining were those who had not taken vaccines but had acquired infection in the recent past few months.

About 61 healthcare workers had not developed adequate antibodies even after taking both the doses.

Similarly, there were 25 workers who had taken a dose but had not developed antibodies.

The remaining who lacked antibodies have not been vaccinated so far.

Out of 500-odd plasma donors who came for donation 14 days to three months after recovery, only 50 per cent were found to be having adequate antibodies. These donors had either lost their antibodies prematurely or did not produce enough.

It could be because of low immunity or less severe infection.

Prof Tulika Chandra, head of the transfusion medicine department, said, "This shows the probability of developing adequate antibodies that also last for a long period through vaccination, rather than acquiring infection in a natural way. The high percentage of antibodies in this group is a good sign, hinting at herd immunity through vaccination."

She explained, "Generally, when a person is infected, memory cells in the body store the information of infection.

Hence, even if antibodies are not formed, it is assumed that memory cells will be able to fight the infection if a person is exposed to the risk again. But the second wave saw many cases of reinfections due to which scientists presumed that memory cells did not work well in them."

These are preliminary results of the study. The target is a sample size of 4,000 which can bring about further revelations. Some of the vaccinated healthcare workers tested in the first round will be tested again later to determine the longevity of the antibodies developed through vaccination.