https://pubmed.ncbi.nlm.nih.gov/34981076/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8722618/
From these two reports, the followings are highlighted,
Infection with Omicron increases the titer of neutralizing antibodies against Delta (by about 4.4imes),
Three doses of the mRNA vaccine keep the neutralizing antibody titer high for all variant strains.
