Recovery from coronavirus may not confer immunity, warn experts

Paris

Even as virologists zero in on the virus that causes COVID-19, a very basic question remains unanswered: do those who recover from the disease have immunity? There is no clear answer to this question, experts say, even if many have assumed that contracting the potentially deadly disease confers immunity, at least for a while. “Being immunised means that you have developed an immune response against a virus such that you can repulse it,” explained Eric Vivier, a professor of immunology in the public hospital system in Marseilles.

“Our immune systems remember, which normally prevents you from being infected by the same virus later on.” For some viral diseases such a measles, overcoming the sickness confers immunity for life. But for RNA-based viruses such as Sars-Cov-2 -- the scientific name for the bug that causes the COVID-19 disease -- it takes about three weeks to build up a sufficient quantity of antibodies, and even then they may provide protection for only a few months, Vivier said. At least that is the theory.

In reality, the new coronavirus has thrown up one surprise after another, to the point where virologists and epidemiologists are sure of very little. “We do not have the answers to that -- it’s an unknown,” Michael Ryan, executive director of the World Health Organization’s Emergencies Programme said in a press conference this week when asked how long a recovered COVID-19 patient would have immunity. “We would expect that to be a reasonable period of protection, but it is very difficult to say with a new virus -- we can only extrapolate from other coronaviruses, and even that data is quite limited.”

For SARS, which killed about 800 people across the world in 2002 and 2003, recovered patients remained protected “for about three years, on average,” Francois Balloux director of the Genetics Institute at University College London, said. “One can certainly get reinfected, but after how much time? We’ll only know retroactively.”