…. recovered patients should continue taking precaution

THE World Health Organisation (WHO) has cautioned world governments and patients who have recovered from COVID-19 that there is no hard evidence to prove that reinfection of the virus cannot happen.

In a recent scientific brief, the WHO cautioned countries against operating as if those recovered can face no new threat and therefore pose no threat to others, as this could add to the spread of the virus.

“At this point in the pandemic there is not enough evidence about the effectiveness of antibody-mediated immunity to guarantee the accuracy of an ‘immunity passport’ or ‘risk-free certificate’,” WHO stated.

It added: “People who assume that they are immune to a second infection because they have received a positive test result may ignore public health advice. The use of such certificates may therefore increase the risks of continued transmission.”

Guyana’s health authorities continue to encourage all Guyanese to take the necessary COVID-19 precautions. It has not made a pronouncement that any person could be immune to the virus.

The WHO said that as new evidence on antibody-mediated immunity becomes available, it will update this scientific brief.

However, it has noticed that some governments have suggested that the detection of antibodies to the SARS-CoV-2 — the virus that causes COVID-19 —- could serve as the basis to enable individuals to return to work assuming that they are protected against re-infection.

“There is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection,” WHO reiterated.

It explained that the development of immunity to a pathogen through natural infection is a multi-step process that typically takes place over 1-2 weeks.

While studies conducted show that people who have recovered from infection have antibodies to the virus, it must be noted that some of these people have very low levels of neutralizing antibodies in their blood suggesting that cellular immunity may also be critical for recovery.

WHO stated that as of April 24, 2020, no study has evaluated whether the presence of antibodies to SARS-CoV-2 confers immunity to subsequent infection by this virus in humans.

Laboratory tests that detect antibodies to SARS-CoV-2 in people, including rapid immunodiagnostic tests, need further validation to determine their accuracy and reliability.

Even so, inaccurate immunodiagnostic tests may falsely categorize people by falsely labelling people who have been infected as negative, or labelling as positive, people who have not been infected.

The Organisation said that these tests also need to accurately distinguish between past infections from SARS-CoV-2 and those caused by the known set of six human coronaviruses.

“Four of these viruses cause the common cold and circulate widely. The remaining two are the viruses that cause Middle East Respiratory Syndrome and Severe Acute Respiratory Syndrome. People infected by any one of these viruses may produce antibodies that cross-react with antibodies produced in response to infection with SARS-CoV-2,” WHO stated.

“Many countries are now testing for SARS-CoV-2 antibodies at the population level or in specific groups, such as health workers, close contacts of known cases, or within households. WHO supports these studies, as they are critical for understanding the extent of – and risk factors associated with – infection. These studies will provide data on the percentage of people with detectable COVID-19 antibodies, but most are not designed to determine whether those people are immune to secondary infections.”