WHO: No proof catching virus gives you immunity

CATCHING coronavirus may not grant you immunity, the World Health Organisation has warned, as there is currently ‘no evidence’ survivors are protected.

Ministers are hoping millions might have already been infected with the virus without showing major symptoms and are now immune. Once a reliable antibody blood test becomes available, they may then return to work to help restart the economy.

But Dr Maria van Kerkhove of the WHO has cast doubt on that plan, saying: ‘Right now, we have no evidence that the use of a serological [blood] test can show that an individual has immunity or is protected from reinfection.’ While the new tests will measure antibody levels, people having antibodies to the virus does not necessarily mean they are immune, she explained.

Antibodies are one weapon the immune system has to fight infection, although there are others in its armoury. Antibodies develop either in response to a particular virus, or in response to a vaccine.

Usually, exposure to a virus confers a degree of immunity. But experience from other coronaviruses – from mild to dangerous – suggests that the human body struggles with the infection.

Professor Sir John Bell, of Oxford University, said: ‘These little critters are really pretty devious in terms of their ability to evade the immune response.’

The SARS epidemic of 2002-03 showed people ‘did not have durable long-term immunity’ to the coronavirus which caused the disease, he said. The virus that causes Covid19, called SARS-CoV-2, is genetically very similar to that which caused the original SARS.

A crucial question is whether a vaccine can produce a long-lasting immune response to a coronavirus when the human body seems to struggle. Prof Bell said: ‘We might get lucky [with a vaccine] and we should be able to measure [its] durability. Seasonal vaccination may be necessary, like with flu.’