There is still no good correlate of SARS-CoV-2 protection. Part of the problem is that even if neutralising antibodies were predictive this would eb strain specific and there are just too many strains out there to be able to measure neutralisation against them to make a consensus view is someone likely to be protected or not against currently circulating and future variants. Our data still suggests that spike IgA even in serum is one of the best predictors of protection against future infection