5 volunteers excluded after +ve antibody test

Naina Mishra

Tribune News Service

Chandigarh, October 3

As many as five volunteers, who had enrolled for the Covishield (Covid-19 vaccine) trials, were found unfit for the study after they were found positive in the antibody test.

Prof Mini P Singh, Department of Virology, the Post Graduate Institute of Medical Education and Research (PGIMER), said, “Among the 66 participants, who were healthy and never experienced any symptom of Covid, five were found positive for IgG antibody test, clearly indicating that they had caught the infection, but were asymptomatic.”

The PGIMER has already screened 66 volunteers ever since it started enrolling candidates for clinical trials of the vaccine. Of these, 42 candidates have been administered the first dose of Covishield (SII-ChAdOx1 nCoV-19) so far.

One of the exclusion criteria for enrolling volunteers for the trial is the immunoglobulin G (IgG) seropositivity to SARS-CoV-2. Prof Mini said, “Among the healthy volunteers, the seropositivity was found to be only 7.6 per cent, implying that most of the tricity population is still not exposed to the virus. In this scenario, it also becomes important to carry out a serosurvey in large scale to see whether people have contracted an infection or not, or is the spread just the tip of an iceberg.”

‘20% of recovered patients had no antibodies’

“The data is at a very preliminary stage as the sample size is small. However, it matches with the findings of serosurvey studies carried out by the Indian Council of Medical Research (ICMR). This is also suggestive of the fact that people are not coming forward to get themselves tested for Covid due to stigma attached with the infection. We found out some individuals did not get themselves tested for the contagion despite being apprehensive of the symptoms. It has been noticed that such individuals also have a good amount of antibody titer (a type of blood test that determines the presence and level (titer) of antibodies in the blood,” said Prof Mini and added that 20 per cent of the recovered patients had no antibodies.

Doctors at the PGIMER have also found that around 20 per cent of the people, who had been cured of the disease, had weak or no antibodies against the SARS-CoV-2 virus. About 66 of the total 80 cured patients showed the presence of antibodies against the SARS-CoV-2 and remaining did not show antibodies.

Prof Mini said, “This is an ongoing study and the results may vary when the numbers will increase. The recovered patients, who did not develop antibodies, despite recovery are around 20 per cent. Usually, antibodies are formed within three weeks of recovery. One of the reasons is that sometimes asymptomatic patients do not form antibodies. There is always a chance of false positive in the Covid-19 testing.”

42 candidates administered first dose

The PGI has already screened 66 volunteers ever since it started enrolling candidates for the clinical trials of the vaccine. Of these, 42 candidates have been administered the first dose of Covishield (SII-ChAdOx1 nCoV-19) so far.