A leading epidemiologist says the Omicron wave may be prolonged because most states eased close contact isolation rules a month too early.

University of Melbourne epidemiologist and surgeon, Professor Nancy Baxter says state health departments should have waited until the viral transmission was lower before removing close contact requirements. 

Even though case numbers were stabilising, ending restrictions now before case numbers came down further, could mean the tail of the wave was prolonged or the plateau was higher, she said.

About one-third of COVID-19 PCR tests were still positive, which would mean there was still a lot of the virus circulating undetected, she added.