RW, thanks for the sources. The Nature article talks about exactly the issue I mentioned – longer lasting protection from B Cells (that will produce antibodies in the future) that are developed both by (at least) mild Covid cases and vaccine. This is indeed hopeful. They have a caveat that variants might block this production of antibodies.
Healthline refers to the paper “Necessity of COVID-19 vaccination in previously infected individuals”. This paper shows 97% effectiveness of mRNA vaccines for those without previous infection and 66%(3x) effectiveness for those with previous infection – the author conclude from the latter that there is no benefit of giving vaccines to previously infected. This judgment is made from the world /WHO perspective that it is better to re-allocate vaccines to poor countries.
My note: High effectiveness of both vaccine and previous infection in this paper comparing to the ones I quoted is due to several factors: other papers I quoted defined previous infection as PCR tests given to everyone. This paper use only highly symptomatic cases as “infected” (those who were sick and went to take a test, with %age of positive test varying over time from 5% to 20% – higher than usual testing). Similarly, they measure 2nd infection as people coming for a test. So, these results are for “at least mild symptomatic COVID”. They also do not seem to adjust for demographics, while acknowledging that unvaccinated were younger (39 v 42 average age).
Bottom line: there is support to say that those with a symptomatic mild case have immunity comparable to vaccines. It could be further enhanced by one does of vaccine – unless you want to ethically donate it to 3rd world. Easy cases may be more risky. All of this pre-Delta.
And, of course, none of these papers suggest any benefit of actually not taking a vaccine and waiting for “natural immunity”.