An Australian meta-analysis suggests third shots can more than double protection against illness from the rapidly spreading variant.
Australian research has found that two-dose vaccination is only partially effective against the Omicron variant and boosters are essential to prevent symptomatic and severe covid-19 infection.
A new preprint paper from the Kirby Institute at the University of NSW estimates that six months post primary course immunisation, vaccine efficacy against Omicron is down to around 40% for symptomatic infection, and 80% against severe infection.
However, a booster dose can increase efficacy from 40% to 86.2% for symptomatic infection, and up to 98.2% for severe disease.
The researchers used previous studies within ADAPT – an ongoing observational cohort study run by St Vincent’s Hospital in Sydney – and a model they had already established of predicting vaccine efficacy based on neutralisation titres.
They also estimate that prior infection with the ancestral SARS-CoV-2 strain provides around 34% protection against symptomatic Omicron infection and 77% protection against severe symptoms.
“Emerging data on the loss of neutralisation against the Omicron variant reveals considerable escape of neutralising responses,” the paper says, “but indicates that high levels of protection to symptomatic and severe infection is likely to be achieved by boosting with existing vaccines that target ancestral spike protein.”
At a news briefing this morning Stuart Turville, Kirby Institute associate professor in immunology and pathogenesis, said the Omicron strain surpassed Beta as the most evasive variant yet.
“What we can see with Omicron is it’s accumulated a fair amount of changes and there’s quite a few changes in key areas, like the spike of the protein that dictates transmissibility and its ability to be inhibited by antibodies that are generated during a vaccine response or previous infection,” Associate Professor Turville said.
