Test-negative, case–control study: Effects of previous infection and vaccination on symptomatic omicron infections.

Effects of Previous Infection and Vaccination on Symptomatic Omicron Infections – New England Journal of Medicine

Commentary: Qatar Omicron-wave study shows slow decline of natural immunity, rapid decline of vaccine immunity – Weill Cornell Medicine

Related:

Hybrid immunity: a combination of vaccination and prior infection probably offers the best protection against COVID – The Conversation

Protection and Waning of Natural and Hybrid Immunity to SARS-CoV-2 – New England Journal of Medicine

SARS-CoV-2 reinfections: Overview of efficacy and duration of natural and hybrid immunity – Environmental Research

Two new studies show vaccination provides additional protection after Covid-19 infection.

Commentary on Twitter

A study in Qatar assessed the effectiveness of previous infection, vaccination, and both against symptomatic SARS-CoV-2 caused by omicron BA.1 and BA.2 and against severe, critical, or fatal #COVID19. https://t.co/bEVD3Y1sUn pic.twitter.com/Y38a0xxead

— NEJM (@NEJM) June 15, 2022