"... There are marked differences in your immune system after a natural infection with
coronavirus and after vaccination... we're no longer starting with zero immunity as the overwhelming
majority of people have either been vaccinated or have already caught the virus.
...Prof Adam Finn, a government vaccine adviser, said over-vaccinating people, when other
parts of the world had none, was "a bit insane, it's not just inequitable, it's stupid".
...There are four key areas to compare vaccine and natural infection with the virus.
Breadth... You get a broader immune response after being infected with the virus than
vaccination... "That means if you had a real humdinger of an infection, you may have better immunity
to any new variants that pop up as you have immunity to more than just spike," said Prof Riley.
Strength... How well it stops infection or prevents severe disease... "Neither gives you
complete protection versus infection, but the immunity you get from either seems to protect
you pretty well from serious illness," said Prof Finn, from the University of Bristol.
Antibody levels are, on average, higher about a month after vaccination than infection. However,
there is a huge gulf in antibodies between those who are asymptomatic (who don't make very much)
and those who get a severe bout of Covid. The biggest immune response comes from people who
caught Covid and were then vaccinated. We're still waiting for data on what happens the other
way round.
Duration... How long does protection last... Antibody levels have been shown to decline over
time, although this may not be important for preventing severe disease. There are "memory
T-cells" that linger in the body, and B-cells remain primed to produce a new flood of antibodies
on demand. There is evidence of immune responses more than a year after infection and vaccine
trials have also showed lasting benefit. "In terms of durability, we're still waiting to see,"
said Prof Peter Openshaw, from Imperial College London.
Location... Where in the body is the immunity... There is a whole different suite of antibodies
(known as immunoglobulin As) in the nose and lungs, compared with those (immunoglobulin Gs)
that we measure in the blood. The former is more important as a barrier to infection. Natural
infection, because it is in the nose rather than a jab in the arm, may be a better route to
those antibodies, and nasal vaccines are being investigated too. Prof Paul Klenerman, who
researches T-cells at the University of Oxford, said: "The location of an infection makes a
difference even if it's the same virus, so we would expect important differences between
natural infection and vaccines."
There is clear evidence that adults who have not had any vaccine dose will have stronger immune
defences if they do get vaccinated, even if they have caught Covid before.
Each time you're exposed, the immune system gets a little bit stronger, and this continues until
old age, when the immune system starts to fail and the infections become a problem again....
bbc.com |
