Estimates of Vaccine Effectiveness against Omicron hospitalization, etc.

[M_T]

Estimates of reduced vaccine effectiveness against hospitalization, infection, 
transmission and symptomatic disease of a new SARS-CoV-2 variant, Omicron 
(B.1.1.529), using neutralizing antibody titers

Omicron increased the risk of hospitalization four to five-fold and increased the risk of symptomatic disease seven to ten-fold for mRNA vaccinees, with similar relative effects for recently vaccinated, or individuals with waned antibody titers. Third doses restored titers and protection to levels similar to waned immunity against Delta. Overall, these analyses indicate that vaccine effectiveness against severe disease is significantly diminished for waned individuals, and protection against infection, symptomatic disease and transmission is nearly eliminated. However, third doses significantly ameliorate these reductions but only restore protection to levels equivalent to waned protection against the Delta variant. The invasion of Omicron is likely to result in widespread infection, and substantial hospitalizations unless widespread boosting of immunity occurs.

(bold and italics are mine)