Wednesday 25 November, 2020

Cayman antibody tests reveal more people had been positive for COVID19

The Cayman Islands has run 994 COVID-19 antibody tests to date. Of these, 2/3 were done at the Health Services Authority and 1/3 were done at Health City Cayman Islands. Chief Medical Officer, Dr John Lee has indicated that the individuals who have been tested are not representative of the general population as they have been those who were either found to be PCR positive or those who were at a higher risk for the virus including healthcare staff and contacts of PCR positives.

These tests have yielded some interesting results, among them is the fact that the rate of antibody positives is exceedingly low which means that there were likely to have not been as many cases in the community as previously thought.

Of the 994 tests that were run:

41 people were found to be positive for antibodies (4.1 per cent of tests run)

33 of those who were found to be positive for antibodies were previously positive on the PCR test

3 of the positives were contacts of people who were positive for the PCR test

5 had no history of being positive on the PCR test and were not contacts of those who were positives

9 people (20 per cent of the COVID19 positive cases) were negative for antibodies even though they were positive on the PCR test

Dr John Lee has indicated that the latter could have happened for one of three reasons:

  1. The individual had the virus but did not have an antibody response
  2. The test was not sensitive enough to pick up the specific antigen in the blood
  3. There was an antibody response but the IgG is not strongly discernable

Levels of antibodies rise and fall at different times after infection. IgG is the last to rise but lasts longest. Levels of antibodies are usually highest a few weeks after infection.

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