Even as virologists zero in on the virus that causes COVID-19, a awfully basic question remains unanswered: do those that endure the disease have immunity?
There is no clear answer to the current question, experts say, whether or not many have assumed that contracting the possibly deadly disease confers immunity, a minimum of for ages.
“Being immunised implies that you’ve got developed an immunologic response against a pestilence specified you’ll be able to repulse it,” explained Eric Vivier, a professor of immunology within the public hospital system in Marseilles.
“Our immune systems remember, which normally prevents you from being infected by the identical virus in a while.”
For some viral diseases such the measles, overcoming the sickness confers immunity forever.
But for RNA-based viruses like SARS-CoV-2 – the scientific name for the virus that causes the COVID-19 disease – it takes about three weeks to create up a sufficient quantity of antibodies, and even then they will provide protection for under some months, Vivier told AFP.
At least that’s the speculation. In reality, the new coronavirus has thrown up one surprise after another, to the purpose where virologists and epidemiologists are sure of little.
“We don’t have the answers to it – it’s an unknown,” Michael Ryan, decision-maker of the planet Health Organization’s Emergencies Programme said during a news conference on when asked how long a recovered COVID-19 patient would have immunity.
“We would expect that to be an affordable period of protection, but it’s very difficult to mention with a replacement virus – we will only extrapolate from other coronaviruses, and even that data is kind of limited.”
For SARS, which killed about 800 people across the planet 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, told AFP.
“One can certainly get reinfected, but after what proportion time? We’ll only know retroactively.”
A recent study from China that has not suffered review reported on rhesus monkeys that recovered from SARS-CoV-2 and didn’t get reinfected when exposed yet again to the virus.
“But that does not really reveal anything,” said Pasteur Institute researcher Frederic Tangy, noting that the experiment unfolded over only a month.
Indeed, several cases from Republic of Korea – one among the primary countries hit by the new coronavirus – found that patients who recovered from COVID-19 later tested positive for the virus.
But there are several ways to clarify that outcome, scientists cautioned.
While it’s not impossible that these individuals became infected a second time, there’s little evidence this is often what happened.
More likely, said Balloux, is that the virus never completely disappeared within the first place and remains – dormant and asymptomatic – as a “chronic infection”, like herpes.
As tests for live virus and antibodies haven’t yet been perfected, it’s also possible that these patients at some point tested “false negative” when of course that they had not rid themselves of the pathogen.
“That suggests that folks remain infected for a protracted time – several weeks,” Balloux added. “That isn’t ideal.”
Another pre-publication study that checked out 175 recovered patients in Shanghai showed different concentrations of protective antibodies 10 to fifteen days after the onset of symptoms.
“But whether that antibody response actually means immunity could be a separate question,” commented Maria Van Kerhove, Technical Lead of the WHO Emergencies Programme.
“That’s something we actually have to better understand – what does that antibody response seem like in terms of immunity.”
Indeed, a bunch of questions remain.
“We are at the stage of asking whether someone who has overcome COVID-19 is de facto that protected,” said Jean-Francois Delfraissy, president of France’s official science board.
For Tangy, an excellent grimmer reality can’t be excluded.
“It is feasible that the antibodies that somebody develops against the virus could actually increase the danger of the disease becoming worse,” he said, noting that the foremost serious symptoms come later, after the patient had formed antibodies.
For the instant, it’s also unclear whose antibodies are stiffer in beating back the disease: someone who nearly died, or someone with only light symptoms or perhaps no symptoms in any respect. And does age make a difference?
Faced with of these uncertainties, some experts have doubts about the wisdom of pursuing a “herd immunity” strategy specified the virus – unable to search out new victims – peters out by itself when a majority of the population is immune.
“The only real solution for now’s a vaccine,” Archie Clements, a professor at Curtin University in Perth, Australia, told AFP.
At the identical time, laboratories are developing a slew of antibody tests to determine what proportion of the population in numerous countries and regions are contaminated.
Such an approach has been favoured in Britain and Finland, while in Germany some experts have floated the thought of an “immunity passport” that will allow people to travel back to figure.
“It’s too premature at this time,” said Saad Omer, a professor of infectious diseases at the Yale School of drugs.
“We should be able to get clearer data very quickly – during a number of months – when there’ll be reliable antibody tests with sensitivity and specificity.”
One concern is “false positives” caused by the tests detecting antibodies unrelated to COVID-19.
The idea of immunity passports or certificates also raises ethical questions, researchers say.
“People who absolutely have to work — to feed their families, as an example – could attempt to get infected,” Balloux.