Ah sorry. Ill copy and paste the whole article.
At Christmas, my teenage daughter gave me the gift of Covid. Our patch of South East London is close to the Kent border, and the new variant virus was rampaging through schools. Fortunately, both she and I had it only relatively mildly – like a nasty cold. In January, when I’d recovered, I volunteered to help with the local vaccine effort, which made me eligible for vaccination.
Friends were terribly jealous of my apparent double Covid-proof status. “Even your antibodies will have antibodies,” said one. Feeling smugly certain that I was bursting with immunity, I didn’t hesitate when I then received a text asking me to donate plasma to the NHS. The idea was that my antibody-rich blood plasma would be infused into people hospitalised with Covid in the hope that this would boost their fight against the disease. I tootled off to a test centre where they took a sample.
The results, a week later, surprised and dismayed me. My antibody level was too low to be useful. They didn’t want me. I felt almost insulted. But more importantly, I wondered if that meant I had not responded to the vaccine. Was it ever going to be safe to hug my mum? Was I even immune to future infection?
My experience comes as a new generation of Covid antibody tests launch onto the market. Costing as little as £50, they look for antibodies that recognise the spike protein on the surface of the coronavirus. While previous tests merely told you if you had any antibodies at all, these new ones reveal the precise levels – or titres. James Monico, co-founder of the non-profit organisation Testing For All, which sells them to consumers, told the New Scientist last week: “A low antibody response means you are more likely to get reinfected and pass it onto someone else.”
So is that true – and are these tests worth having?
Professor George Kassiotis knows a thing or two about viruses. He is head of the laboratory of retroviral immunology at the Francis Crick Institute, London and a professor of retrovirology at Imperial College London. He says that the tests are “effectively meaningless. We cannot equate antibody levels with immunity in people”.
This is because, he says, “antibodies are not the be all and end all of immunity”. For example, “with Covid vaccines we can show that protection kicks in around ten days after the first dose. This is well before we can detect any neutralising antibodies in the majority of vaccinated people.”
And if you, like me, had a mild Covid infection, your antibody levels will be much lower than if you’d had a severe infection or have been vaccinated. Though there is no doubt, says Prof Kassiotis, that vaccination produces a stronger antibody response than infection.
Antibodies are part of a complex chain of events that is triggered when the body is exposed to a virus, he says. “Our immune system has two phases. When we first become infected with the virus, the first line of defence is our ‘innate’ and non-specific immune response, which uses immune cells to slow progress of the virus and even prevent it causing symptoms. This causes the inflammatory symptoms of swelling, pain and fever.”
If this response is insufficient to tackle the virus, back-up is summoned in the form of your body’s adaptive immune system, which creates ‘memory cells’ known as B cells and killer T-cells.
If the virus continues to spread, says Prof Kassiotis, “B cells bind to the virus and make antibodies that are specific to that virus. It can take up to ten days for the body to multiply enough B cells to overwhelm the virus.”
In other words, antibodies are not the only weapon our immune system uses to beat an infection – and are certainly not a reliable measure of a person’s level of protection against Covid, because we’ve no idea what the required level would be.
He says, “Sometimes people with very high antibody levels are vulnerable to infection with a different strain or even the same strain of coronavirus.” And we still don’t know how antibody levels affect the risk of transmitting the virus to other people.
That’s not to say that antibodies are irrelevant. “Generally, you can say that on a population level, if you have antibodies, you are more likely to be protected against Covid-19,” says Kassiotis. “And it does seem that people with high levels of antibodies are better at recognising new variants.” There is also some evidence that levels of antibodies reduce more slowly in people who had high levels to start with.
“But this doesn’t tell us anything about an individual,” says Prof Kassiotis. “While more antibodies is usually better, without a defined cut-off point, above which people are protected, and below which they are at risk, I can’t see the point of testing.”
There are many factors that could affect your antibody levels after infection or vaccination. People with immune deficiency diseases such as HIV won’t make antibodies. Nor will those undergoing certain cancer treatments.
We also know that older people make fewer antibodies when infected with Covid-19, as the ageing immune system is less effective.
A new study published in The Lancet has found that while over 80 per cent of people who had the original strain of the disease were protected from reinfection for at least six months, this fell to just 47 per cent in people over 65. Reinfection, though, is generally rare. Of 11,068 people who tested positive during the first surge, only 72 tested positive again during the second.
However, says Prof Kassiotis, this doesn’t seem to apply with vaccination. “Vaccines seem equally effective in older age groups. It seems that even if vaccinated older people have low antibodies generally, their levels will rapidly increase if they become infected with Covid-19.”
Though antibody tests are undoubtedly an appealing idea as we look to the roadmap to freedom, Prof Kassiotis says they could be dangerous. “If your test shows high antibody levels after infection, you might think you are invincible and take more risks or even decline the offer of vaccination. On the other hand, someone might have low antibody titres after vaccination and worry that they are not protected and that could also be wrong.”
As for me, I was reassured to learn that my failure to donate plasma did not mean I had freakishly low levels. Of everyone invited to donate convalescent plasma, only 10 per cent met the high antibody threshold. These were more likely to be men who had been hospitalised with the disease.
“Protection can exist even if tests can no longer detect antibodies,” says Prof Kassiotis. “The numbers never go down to where they were before our body was introduced to the virus. They remain elevated for our lifetime. We call this ‘immunological memory’.
“If you do get reinfected, it is highly unlikely that the illness will be worse than the first time. Neither will you be totally defenceless – even years after infection or vaccination.”