I’ve also heard that past infection confers marginal immunity even in the presence of vaccination.
What do you mean by “marginal”? The most common meaning is “low,” and if that’s what you mean, you really need to know it’s false. But I guess you mean “additional.” That’s a pretty weird usage, though, because infection isn’t a margin that is easy to control, particularly if it comes before the vaccine (it would make more sense to switch the words “infection” and “vaccination”). There are lots of studies trying to measure how much protection infection + one shot gives. The most interesting is one that claimed that it provided substantial protection not just against sars-2 variants, but even against the quite distant sars-1. I’m not sure anyone has tested against delta, but protection against sars-1 is a pretty good substitute.
So why is this combination so broadly useful? One possibility is that actual infection is so different from vaccination that the body responds broadly, to encompass both. This possibility doesn’t give much practical advice, although mixing vaccines would provide a little diversity. Another possibility infection is just like a vaccination, but came much earlier and the long interval (8 months) produced broad immunity. Indeed, memory cells diversify over time. If this is the mechanism, then an additional dose could be valuable, not because it is additional, but because it is so much later. The time between doses might be more important than the number of doses, particularly for broad immunity, ie, for variants. Since the UK already has a longer vaccine interval than the rest of the world, they should be better protected against delta, so their success so far might not be such good news for the rest of the world.
What do you mean by “marginal”? The most common meaning is “low,” and if that’s what you mean, you really need to know it’s false. But I guess you mean “additional.” That’s a pretty weird usage, though, because infection isn’t a margin that is easy to control, particularly if it comes before the vaccine (it would make more sense to switch the words “infection” and “vaccination”). There are lots of studies trying to measure how much protection infection + one shot gives. The most interesting is one that claimed that it provided substantial protection not just against sars-2 variants, but even against the quite distant sars-1. I’m not sure anyone has tested against delta, but protection against sars-1 is a pretty good substitute.
So why is this combination so broadly useful? One possibility is that actual infection is so different from vaccination that the body responds broadly, to encompass both. This possibility doesn’t give much practical advice, although mixing vaccines would provide a little diversity. Another possibility infection is just like a vaccination, but came much earlier and the long interval (8 months) produced broad immunity. Indeed, memory cells diversify over time. If this is the mechanism, then an additional dose could be valuable, not because it is additional, but because it is so much later. The time between doses might be more important than the number of doses, particularly for broad immunity, ie, for variants. Since the UK already has a longer vaccine interval than the rest of the world, they should be better protected against delta, so their success so far might not be such good news for the rest of the world.