How effective are the current COVID-19 vaccines as the virus continues to evolve?

Embargoed until: Publicly released: 2024-05-31 09:00

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The COVID-19 vaccines currently available in Australia are still effective, especially against hospitalisation and death, but their effectiveness has dropped as new variants come through, according to research from the US. The team compared COVID-19 outcomes in about 1.8 million people in the US, about 12% of whom had been boosted or vaccinated with one of the newer vaccines targeting subvariant XBB.1.5 (the vaccines currently preferred in Australia.) Comparing with the general population, which includes unvaccinated people and people vaccinated with earlier versions of the vaccines, the researchers calculated the XBB.1.5 vaccines were 52.2% effective against symptomatic infection after four weeks, down to 32.6% and 20.4% at 10 and 20 weeks respectively. Effectiveness against hospitalisation at four and 10 weeks respectively was 66.8% and 57.1%, the researchers say, and effectiveness against death was higher but less certain because there were very few deaths. They say over the course of the study, effectiveness appeared to reduce somewhat as newer, non XBB.1.5 variants began spreading.