COVID Q&A: immunity breakthrough is encouraging, but the crisis is far from over

Scientists hail discovery that people infected with the virus may have lasting immunity.

A recovered COVID-19 patient donates blood plasma for research into coronavirus antibodies, as studies have shown for the first time that antibodies can protect against reinfection. Picture: Getty

Scientists are hailing “very encouraging” signs that people infected by the coronavirus could have lasting immunity. Experts had feared that those hit by the virus could face repeat attacks as the body’s defences waned. Now they are beginning to answer the key questions – can we become immune to a disease that has killed almost 800,000 people; how close are we to herd immunity; and what does it mean for the much-feared second wave?

What’s new?

Studies have shown for the first time that antibodies can protect against coronavirus reinfection. Even those who have had asymptomatic or mild cases may have immunity. They also found that T-cells and B-cells, part of the body’s immune response, remain in the blood as antibody levels start to decline.

The findings come from researchers at Arizona University, Washington University, the Karolinska Institute in Sweden and Harvard Medical School, among others. They suggest that people who have been infected and those who will be vaccinated can have effective protection.

“This is a good news story,” said Peter Openshaw, professor of experimental medicine at Imperial College London.

He was not involved in the research but is co-leading one of the world’s largest studies of the immune response of virus patients.

A scanning electron microscope shows SARS-CoV-2 (yellow)—also known as 2019-nCoV, the virus that causes COVID-19—isolated from a patient, emerging from the surface of cells (blue/pink) cultured in a US health lab. Picture: AFP

How long could immunity last?

“At least several months after Sars-CoV-2 infection,” reported the Arizona team. But this is probably an underestimate. Immunity “could last significantly longer”, Openshaw said. “You could get significant protection for at least six months or a year.” The pandemic is not a year old yet, so without 12 or 24 months of following up patients it is impossible to say how long immunity will last.

Even so, the findings are “very encouraging”, said Dr Alison Whitelegg of the Association for Clinical Biochemistry and Laboratory Medicine’s immunology professional committee. “This positive news matters, because antibody studies are very likely to underestimate the immunity in a population that has had a huge exposure to COVID-19, such as London must have done in March when very little testing was available. It also provides an explanation for why we are not seeing local spikes in London.”

Does this good news reduce the threat of a second wave?

“A significant second wave is less likely in places where there was a high rate of infection,” said Whitelegg. But while those already infected may have immunity, a second wave is a danger to others.

Dr Jenna Macciochi, an immunologist at Sussex University, said: “We need to keep in perspective the number of people who have had the virus and the proportion of individuals like the elderly who may still not be able to develop robust and durable immunity even if they have been infected.”

Openshaw is certain the crisis is far from over: “My very strong feeling is that we need to maintain a degree of caution and low levels of infection, because as we enter autumn and winter there is every prospect that we are going to get a big bounce back of the coronavirus and I think we’re all very afraid that it’s not over yet. It’s too early to drop our guard.”

“Individuals like the elderly may still not be able to develop robust and durable immunity even if they have been infected”, says Dr Jenna Macciochi, an immunologist at Sussex University. Picture: Getty

Will a second wave occur?

Cases are surging in many countries, such as America and India, which are still in their first wave, while others that managed to suppress the first wave of outbreaks are seeing infections rise again.

In recent days Germany, Spain, Italy and France have recorded their highest numbers of daily cases since the spring and the World Health Organisation (WHO) has warned of a resurgence in Europe. Hans Kluge, director-general of the WHO’s Europe office, said the wave of new cases was “due in part to the relaxation of public health and social measures . . . people have been dropping their guard”. Other countries that have seen a resurgence include Israel, Peru, Australia and Japan.

The UK is among countries that have imposed local lockdowns. But some scientists believe a second wave here is inevitable. Professor Sir John Bell, regius professor of medicine at Oxford, said a “really bumpy” winter was on the way, especially with the additional risk of flu.

“My bet is that we will get a second wave and the vaccines won’t get here in time to stop the second wave,” he said.

What about herd immunity?

Experts insist we are not even close. “Even in areas of the country where there’s a relatively high rate of antibody positivity, 80 per cent-90 per cent of the population are still vulnerable – in other words, they haven’t been infected,” said Openshaw. Whitelegg said a vaccine was still needed.

A handout picture provided by the Russian Direct Investment Fund shows a vaccine against the coronavirus disease, developed by the Gamaleya Research Institute of Epidemiology and Microbiology in Moscow. Picture: AFP

Bell suggested it might be easier to achieve herd immunity if lots of people have T-cell immunity. Some believe T-cell response could be a more reliable indication than antibody testing of how the virus is spreading.

T-cells come from stem cells made in bone marrow early in life. They play a key role in getting rid of infections. Some are helper T-cells, which help to activate B-cells to make antibodies. Helper T-cells “trumpet” bad news such as the arrival of the coronavirus, Openshaw said: “They’re a bit like the town criers of the immune system.”

They direct killing operations or kill infected cells directly. Once it is all over, most T-cells die but some go on to form memory T-cells that will be quick to respond to the same infection.

Antibodies, meanwhile, are proteins that help to neutralise the coronavirus. They “act rather like putting ketchup or chilli sauce onto bland food – they make foreign material very tasty for the immune system”, said Openshaw.

Bell said: “People calculating herd immunity I don’t think assumed that we would have this level of T-cell immunity in the population.

“If lots of us have got T-cell immunity that largely protects us from the disease, we may be closer to herd immunity than we originally thought.”

The team at the Karolinska Institute said T-cells would probably “prove critical” for long-term immune protection against COVID-19. Importantly, this included people who had mild or asymptomatic infections: “Our collective dataset shows that Sars-CoV-2 elicits robust, broad and highly functional memory T-cell responses, suggesting that natural exposure or infection may prevent recurrent episodes of severe COVID-19.”

The Times