For some of us, Covid is just a sniffle – not even enough to make you go digging around in the bathroom cabinet to see if there is a lateral flow test hiding in there. But scientists specialising in our immune system warn Covid is still causing stonking infections that may be worse than before and knock us out for weeks. So what is going on?
By James Gallagher, Inside Health presenter, BBC Radio 4, 17 December 2023
Article extracts
How we fare after being exposed to Covid comes down to the battle between the virus itself and our body's defences. The earliest stages are crucial as they dictate how much of a foothold the virus gets inside our body, and how severe it is going to be. However, waning immunity and the virus evolving are tipping the scales.
Prof Eleanor Riley, an immunologist at the University of Edinburgh, has had her own “horrid” bout of Covid that was “much worse” than expected. She told me: “People's antibody levels against Covid are probably as low now as they have been since the vaccine was first introduced.”
Antibodies are like microscopic missiles that stick to the surface of the virus and stop it from infecting our body's cells. So, if you have lots of antibodies, they can mop up the virus quickly and any infection will hopefully be short and mild. “Now, because antibodies are lower, a higher dose [of the virus] is getting through and causing a more severe bout of disease,” Prof Riley says.
Antibody levels are relatively low because it has been a long time since many of us were vaccinated (if you are young and healthy you were only ever offered two doses and a booster) or infected, which also tops up immunity. Prof Peter Openshaw, from Imperial College London, told me: “The thing that made the huge difference before was the very wide and fast rollout of vaccines – even young adults managed to get vaccinated, and that made an absolutely huge difference.”
This year even fewer people are being offered the vaccine. Last winter, all over-50s could have one. Now it is only the over-65s, unless you are in an at-risk group. Prof Openshaw says he is not a “doomster”, but thinks the result will be “a lot of people having a pretty nasty illness that is going to knock them out for several days or weeks”.
Antibodies and T cells
Antibodies are highly precise as they rely on a close match between the antibody and the part of the virus to which they stick. The more a virus evolves to change its appearance, the less effective the antibodies become. Prof Openshaw said: “The viruses circulating now are pretty distant immunologically from the original virus which was used to make the early vaccines, or which last infected them. A lot of people have very little immunity to the Omicron viruses and their variants…”
If you are feeling rough with Covid – or rougher than you have done before – it could be this combination of waning antibodies and evolving viruses. But this does not mean you are more likely to become critically ill or need hospital treatment. A different part of our immune system – called T-cells – kick in once an infection is already under way and they have been trained by past infections and vaccines.
T-cells are less easily befuddled by mutating viruses as they spot cells that have been infected with Covid and kill them. “They will stop you getting severely ill and ending up in hospital, but in that process of killing off the virus there's collateral damage that makes you feel pretty rough,” says Prof Riley. Relying on your T-cells to clear out Covid is what results in the muscle pain, fever and chills…
Prof Openshaw is clear “we are not there yet” with Covid, but “with repeated infection we should build up natural immunity”. In the meantime will some of us have to suck up a grotty winter? “I fear so,” says Prof Riley.