Basically no theory about high prevalence of previous infection has survived the test of time, so I think to say something like 'infecting previously recovered people much more vigorously' takes some solid evidence.
I was not concerned about all previous reinfection reports--- after all, anything will happen sporadically.
But I believe recent immune-escape variants are a much higher risk here. Vaccines generate a much higher antibody titer and a much broader complement of antibody responses than natural infection, and still are noticeably less effective against emerging variants.
Waning immunity also will contribute to this concern: reinfection gets more likely with time even without variants.
I believe that even if one is reinfected, one is still partially protected against severe illness by the remaining antibody complements and other means, e.g. t-cell mediated immunity.
Mind you, I don't think this is a huge absolute risk. I just think it's significant enough to be a significant confound for those of us trying to guess what Rt would be with a return to baseline behavior, and enough for people who've "had it" to be less protected than they might expect.
Which emerging variants are you talking about? The Twitter thread I link above talks about the variants that are spreading a lot and from what I see, experts are calm about the level of effectiveness of the vaccines against them.
E.g. in Israel, B.1.351 represented ~5% of dual dose vaccine breakthrough events when it was at a prevalence of less than 1% in the population. This means that B.1.351 is better at causing infection of people with the vaccine than the previously prevalent variants.
This is despite people with the vaccine having higher neutralizing antibody titers against B.1.351 than people naturally infected with previous strains.
Therefore it seems very likely to expect that B.1.351 will also cause reinfection at higher rates than we've been used to, since it appears that people with the vaccine are more protected than people naturally infected. This is especially true if people who were infected earliest have their immune responses start to wane.
Again: I don't think this is a huge absolute risk. I just think it's significant enough to be a significant confound for those of us trying to guess what Rt would be with a return to baseline behavior, and enough for people who've "had it" to be less protected than they might expect.
What's sad is we have enough evidence to show people they need a vaccine to prevent re-infection, yet it doesnt seem to move the needle for many where vaccines are plentiful
Basically no theory about high prevalence of previous infection has survived the test of time, so I think to say something like 'infecting previously recovered people much more vigorously' takes some solid evidence.