[Petrochemicals (OP)]

If you have survived the Wuhan strain of sarscov2 does it mean you have natural protection against the cockney or South Africa strains ?

[evan_au]

No protection is perfect.
- Antibody levels naturally decline over time, so it is possible that a couple of years later, you might get reinfected by the same strain.
- Each person will generate a unique cocktail of antibodies to a COVID-19 infection. Some of these antibody strains will recognize the new variant, and some won't (or will have reduced affinity). If you are unfortunate, your individual cocktail of antibodies won't recognize the new variant, and you are likely to be infected by some of the new strains. But some people will be lucky...

The best protection is to have a low level of virus circulating, so you are less likely to be exposed to it.
- And as some have observed, if there is virus circulating somewhere in the world, it will be circulating everywhere in the world...

[set fair]

Evan is right. There are some 20 antibody epitopes on the D614G variant which dominated the first wave outside China. An antibody epitope is a place on the virus to which an antibody can attach and each individual will produce only some of these. There are T cell epitopes too but being harder to study we don't know the situation with them.

Falling antinody levels will lead to a person being suseptible to reinfection and it is pot luck which epitopes have gone due to mutation. Weak immunity in an individual who has been reinfected can lead to the virus mutating to evade that persons antibodies. There is also the possibility that the individual will only make more of the original antibodies rather than make antibodies to the new epitopes of the new variant - we don't know how widespreasd that is and if we wait and see rather than investigate, we won't know until the summer, when the first vaccinees are coming up to 4 or 5 months since their second jab.

[Petrochemicals (OP)]

I was led to believe antibodies fell after a period whilst Tcell retained the memory to reproduce antibodies if needed. I do not think it would be healthy for a human to have a sufficient level of antibodies to counter  every pathogen ever encountered.

[Bored chemist]

I do not think it would be healthy for a human to have a sufficient level of antibodies to counter  every pathogen ever encountered.

I considered the alternative and came to the conclusion that having sufficient antibodies to all the diseases we encountered would be a great deal healthier than not doing so.

I have the advantage of understanding the word "sufficient" and knowledge that we can make more antibodies if we need to.

[set fair]

I was led to believe antibodies fell after a period whilst Tcell retained the memory to reproduce antibodies if needed.

So was I, but now they are not sure and it may be down to memory B cells. Antibody levels look like they are at least a marker for immunity in covid and the simplest explanation is that high enough levels are protective. I think revaccination 5 months after the second jab makes good sense just to keep up the antibody levels.

[evan_au]

I do not think it would be healthy for a human to have a sufficient level of antibodies to counter  every pathogen ever encountered.

Antibodies have a half-life of about 2 weeks in the body.

I agree that there must be some cost to having lots of white blood cells continually churning out high levels of every antibody you have ever needed, as if you had a simultaneous acute infection to every disease to which you were ever exposed!

So it makes sense for those white blood cells to get quieter after the infection has passed, but ready to reactivate if later exposed to the same pathogen.

In my simple understanding, having once been exposed to a pathogen:
- Circulating neutralizing antibodies will prevent a new infection, if they are still at a high enough level in the body.
- Other antibodies may not prevent an infection, but will notify the immune system that an infection is underway, and ramp up an immune response.
- Killer cells will detect and destroy infected human cells, preventing them from budding off more virus particles.