Very interesting article on how good Pfizer and AZ vaccines are against Delta and Beta. The PDF can be downloaded here that I'm quoting from: www.nature.com/articles/s41586-021-03777-9
Looks like 4 weeks post second dose AZ is the sweet spot (a thread or two back, we were wondering how long):
With Pfizer, 13% of individuals neutralized the variant Delta after a single dose. 81 to 100% of individuals neutralized any of the four stains after the second dose, at W8. This fraction remained stable at W16, with the exception of variant Beta, which was neutralized by only 46% of the
individuals. 74% and 61% of individuals that received a single dose of AstraZeneca vaccine neutralized D614G and Alpha strains, respectively. This fraction sharply dropped with Beta and Delta variants, which were inhibited by only 4 and 9% of the sera. Four weeks after the second dose
of AstraZeneca, 95-100% of individuals neutralized the four strains.Therefore, a single dose of Pfizer or AstraZeneca was either poorly or not at all efficient against Beta and Delta variants. Both vaccines generated a neutralizing response that efficiently targeted variant Delta only after the second dose.
And for unvaccinated who had covid then later got one dose (earlier in article but new interesting to me so I only just decided to copy it):
Between 76% and 92% of the individuals neutralized the
four strains at M6. The fraction of neutralizers was lower in the second cohort at M12, a phenomenon which was particularly marked for Beta and Delta. 88% of individuals neutralized Alpha and only 47% neutralized Delta. After vaccination, 100% of convalescent individuals neutral-
ized the four strains (Extended Data Fig.7c). Thus, variant Delta displays enhanced resistance to neutralization
by sera from unvaccinated convalescent individuals, particularly one year after infection.