Covid-19 immunity: Can you catch it again?

Monday July 27 2020

 

By John Namkwahe jnamkwahe@tz.nationmedia.com

Despite winning the battle against the deadly coronavirus (Covid-19), Fred Kasalamba, 29, from Dar es Salaam, still adheres to the given health guidelines to prevent himself from contracting the novel virus again—as some scientists in the world have warned that a recovered Covid-19 patient can catch the virus again.

Fred was first diagnosed with the viral infection [coronavirus] in May this year when he visited a local hospital in the city for treatment.

The hospital then transferred him to a designated Covid-19 hospital located at Ilala District in Dar es Salaam where he was admitted for treatment.

“I experienced difficulty in breathing and chest pain. At the hospital, I was prescribed medicines to relieve fever and chest pains,” says Fred in an interview with Your Health.

Following prolonged medications, Fred was discharged from the hospital and returned home at Kinondoni.

However, the doctor who attended him had instructed him to stay in a separate room from other family members for a while and keep a healthy lifestyle at home.

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“The doctor had also instructed me to rest, continue drinking plenty of fluids, and eat nutritious food,” says Fred.

Can you catch coronavirus twice?

Coronavirus is a completely new infection in people. Nobody had immunity to the virus at the start of the pandemic, but immunity is the key to getting life back to normal, the scientists argue.

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 for an “immunity passport” or “risk-free certificate” that would enable individuals to travel or to return to work assuming that they are protected against re-infection.

Studies suggest it takes around 10 days to start making antibodies that can target the coronavirus and the sickest patients develop the strongest immune response.

If the adaptive immune response is powerful enough, then it could leave a lasting memory of the infection that will give protection in the future.

However, the World Health Organisation (WHO) says there is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection.

WHO continues to review the evidence on antibody responses to SARS-CoV-2 infection.

“It is not yet scientifically proven. Work is still in progress,” says WHO Representative to Tanzania, Dr Tigest Mengestu in an interview with Your Health.

This is backed up with recent new cases of Covid-19 pandemic reported in Uganda whereby the scientists have revealed that four people, who recovered and were discharged from hospital following Covid-19 infection, have tested positive again, Your Health understands.

However, the scientists said they were still investigating to find out whether this was being caused by re-infection or the test kits used to declare the said patients negative were faulty.

Dr Misaki Wayengera, the Head of the scientific advisory committee from Uganda’s Ministry of Health was recently quoted saying, “The exact reason why the patients are testing positive again cannot be established. And we don’t want to rule out the fact that someone can get re-infected but we think the tests are probably picking up dead viruses.”

Further saying, “The test we use can pick up RNA (ribonucleic acid) from a dead virus. But even if someone has recovered, it takes time before the immune system removes virus RNA from the body,” he said, adding that testing someone again may show them still having the virus.

What it might be

In Tanzania, Prof Yunus Mgaya, Director General at National Institute for Medical Research (NIMR) says the circulated claims on Covid-19 sufferers who recovered and then getting sick again is yet to be proved scientifically, however, he articulates that the positive results from people who recovered could be explained by the sensitivity of the Polymerase chain reaction (PCR) machine which can detect viral particles from infected cells that have been killed by the immune system (T cells).

“The cells which are incubating the coronavirus, are searched throughout the entire body and killed by the T-cells until the last virus is dead. So if we do a PCR corona test on an immune person (recovered), it is not a virus that is detected, but a small shattered part of the viral genome or dead particles,” Prof Mgaya elaborates.

Adding, “The test comes back positive for as long as there are tiny shattered parts of the virus left. Even if the infectious viruses are long dead, a corona test can come back positive because the PCR method multiplies even a tiny fraction of the viral genetic material enough [to be detected].”

That’s exactly what happened when there was the global news, even shared by the WHO, that 200 South Koreans who already went through Covid-19 were infected a second time and that there was therefore probably no immunity against this virus.

The explanation of what really happened and an apology came only later when it was clear that the immune Koreans were perfectly healthy and only had a short battle with the virus. The crux was that the virus debris registered with the overly sensitive test and therefore came back as “positive”, Prof Mgaya recalls.

The NIMR boss further recommends that the laboratory test (PCR) with its extreme sensitivity is perfect to identify whether the virus on the recovered person is still alive or infectious.

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

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

Adding that inaccurate immunodiagnostic tests may falsely categorise people in two ways.

The first is that they may falsely label people who have been infected as negative and the second is that people who have not been infected are falsely labelled as positive, saying both errors have serious consequences and will affect control efforts.

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 and WHO supports these studies, as they are critical for understanding the extent of – and risk factors associated with – infection, saying 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 or not.

Other considerations

The WHO argues that 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.”

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 Covid-19 transmission.

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