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Infectious Diseases

Updated 24 April 2020

Scientists unsure about immunity after recovery from Covid-19

We might know a bit more about the virus than we did months ago, but scientists are still uncertain whether we have immunity once we've recovered from Covid-19.

Even as scientists are slowly learning more about the new coronavirus, the virus which causes Covid-19, there are still many grey areas.

One of these is whether someone who became infected with the new coronavirus and contracted Covid-19 will be immune against the virus.

Experts can’t provide a clear answer at this stage, even though it’s assumed that once you get ill from a virus, you acquire immunity, even if it's just for a short while.

"Being immunised means that you have developed an immune response against a virus such that you can repulse it," stated Eric Vivier, a professor of immunology in the public hospital system in Marseilles in a news report.

Immunity may be short lived

"Our immune systems remember, which normally prevents you from being infected by the same virus later on."

Some illnesses such as measles leave you with a lifetime immunity when you recover, but in the case of RNA viruses such as the new coronavirus, the body takes a bit longer to create a sufficient response.

According to Vivier, antibodies can take up to three weeks to be produced, and even then their ability might be short-lived – as little as a couple of months.

"We do not have the answers to that – it's an unknown," said Michael Ryan, executive director of the World Health Organization's Emergencies Programme in a press conference this week as a response to the question of how long immunity against the new coronavirus can last.

What is the case with false negatives?

Several patients in South Korea who recovered from Covid-19 tested positive again after a few weeks. While experts said that it’s probable that they could have been re-infected, there is not enough evidence to back this up.

Instead, it is believed that the virus never disappeared in the first place and remained dormant. It is also believed that, because tests haven’t been perfected yet, these cases may have tested negative in the past while the pathogen was present.

"That suggests that people remain infected for a long time – several weeks," stated Francois Balloux director of the Genetics Institute at University College London

"But whether that antibody response actually means immunity is a separate question," commented Maria Van Kerhove, Technical Lead of the WHO Emergencies Programme. That's something we really need to better understand – what does that antibody response look like in terms of immunity."

"We are at the stage of asking whether someone who has overcome Covid-19 is really that protected," said Jean-Francois Delfraissy, president of France's official science advisory board.

What can be done?

Experts are of the opinion that the only real solution in this case would be a vaccine. While there are at least 70 vaccine candidates in pre-clinical and clinical evaluation phases, they probably won't be available for months.

Laboratories are also hard at work to create antibody tests to see what proportion of people in various areas have been infected.

But even now, existing antibody tests may not be that accurate and can result in false positives.

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