While the “overwhelming majority” of recovered coronavirus patients are believed to develop antibodies, it remains unclear if this means they are immune to re-infection, England’s deputy chief medical officer has warned.
It is hoped that widespread antibody testing could eventually help the government manage the pandemic, with some ministers reportedly keen to pursue the controversial idea of “immunity passports”.
But during Downing Street's briefing on Monday, Jonathan Van-Tam warned “we just haven’t had this disease around on the planet in humans for long enough” to know how long Covid-19 antibodies last or whether they provide immunity against a second wave of infection.
Antibodies produced in response to other human coronaviruses, such as the common cold, ”don’t persist necessarily for years and years and years”, he said, adding: ”We can’t make the science go any faster than how quickly our bodies go in terms of maintaining the antibodies.
“Like everybody else in the world we just have to be patient and cautious until we get those answers.”
It came as health secretary Matt Hancock announced the UK was in talks with pharmaceutical giant Roche over the large-scale roll-out of a new antibody test it has developed with “near-100 per cent” accuracy.
The Swiss-based firm has said it is ready to ramp up production of its Covid-19 antibody test to “double-digit millions per month” over the course of May for use by healthcare services around the world.
It is understood that the test – which is currently being independently valued by Public Health England – could be in use in the UK within weeks, helping officials better establish the true spread of coronavirus.
In a nod to the government’s past purchase of 17.5 million sub-standard home test kits, Mr Hancock said: “There has been false hope before in antibody testing and so we’ll make announcements when we’re absolutely ready.”
Referencing the uncertainty over whether antibodies are a true sign of immunity, he conceded that he himself – having tested positive for the virus in March – would not yet be “comfortable” being in a crowded room.
“I very much hope that the science shows that the people with antibodies, who have tested positive for having antibodies, have a low risk of transmitting the disease and a low risk of catching it," he said.
But “until we know that’s the case we can’t be sure of it, we can’t base a policy decision on it” and he could not be comfortable in a crowd because “that might trigger a rise in the number of infections if the science turns out to be wrong”.
On Saturday, deputy chief medical officer for England Dr Jenny Harries said: “The World Health Organisation position is very similar to the one we would have, which basically says we actually don’t have enough information yet to be very clear on the immune status.”
However, global hopes for immunity received a boost last week from South Korea, after it emerged that a number of patients thought to have re-contracted the virus had in fact returned false positives.
In the earlier stages of the pandemic, reports from South Korea, China and Japan claimed that hundreds of discharged patients had tested positive after recovering, sometimes weeks after being allowed to leave hospital.
But last Wednesday, a South Korean expert panel concluded that dead virus fragments were the likely cause of more than 290 people in the country testing positive again after their recovery.
Antibodies are also key to another promising trial underway in the UK as of this weekend, after encouraging results in Chinese hospitals suggested it can reverse the fortunes of severely ill patients.
Convalescent plasma therapy sees coronavirus sufferers given a transfusion of blood plasma from recovered patients – containing antibodies which have learned to successfully fight a virus – and has been used experimentally since the 1800s, notably during the 1918 Spanish flu epidemic.
The treatment has since been used to treat Sars, Mers and Ebola, and was recently found to be “a promising rescue option” for severely ill Covid-19 patients in Wuhan and Shenzhen pilot studies.
Additional reporting by PA
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