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After in-house GHA screening programme, Govt rethinks its plans for anti-body tests

Eyleen Gomez

The Gibraltar Government is reconsidering its plans to carry out antibody tests on the entire population after an initial screening among GHA frontline workers showed a low prevalence of Covid-19 antibodies.

The antibody tests on GHA staff were a pilot scheme and a precursor to rolling out the screening to the rest of the community. But the initial results are disappointing and have prompted the government to rethink its plans.

Of the 1,247 antibody tests carried out over the past two weeks in the GHA, only 18 were found to be positive for Covid-19 antibodies, which equates to 1.4% of those tested.

Additionally, about half of those frontline workers who had tested positive for Covid-19 and had since recovered later returned negative results in the antibody tests.

That raised questions both about the reliability of the tests and about the longevity of antibodies and any immunity created by the body after recovering from the virus.

Antibody tests are different to the swab tests that have been carried out to date in the community.

Swab tests offer a binary result that confirms whether a person has the virus at the time they are tested, and as such provide a limited snapshot of who is infected at any given time.

Antibody tests, on the other hand, detect Immunoglobulin G [IgG], an antibody produced by the body after it has come into contact with a new infection such as Covid-19.

As such, the antibody test should have offered insight into how many people in the GHA have had the virus without realising it and developed a degree of immunity to it.

“This is an issue on the credibility of the tests in terms of what percentage of clear, correct results we are getting from the tests,” Chief Minister Fabian Picardo said during yesterday’s weekly press briefing at No.6 Convent Place.

“It is clear that this is an issue we need to keep under review and, I think, around the world these issues are manifesting themselves in respect of antibody testing.”

Mr Picardo said the Government will now wait for Public Health advice on whether “testing the whole population will have any value.”

“We have a low level of measurable antibodies in this specific group,” Mr Picardo said, referring to the GHA workers who had been tested.

“Although GHA staff are not representative of the whole population, it does demonstrate the understanding all along that the picture of immunity is complex and comprises of antibodies, cellular immunity and many other factors.”

“We now need Public Health advice as to whether testing the whole population will have any value with such a low prevalence of the virus and the antibodies, especially there, in the GHA, on the front line, where we might have expected to find more.”

He explained that the antibodies arise between three to four weeks after symptoms show and fade four to six weeks after that.

“While it does not mean immunity fades, it implies that the immune response to the core protein does fade and quickly,” Mr Picardo added.

Mr Picardo said the Government had ring-fenced 35,000 antibody tests but these were delivered and paid for in batches, with the current 4,000 in stock due to expire in mid-July.

With the remaining 4,000 tests in stock, the Government is considering to “age stratify” the population and then sample a representative 10% to provide more research data.