New antiviral drugs prevent COVID-19 from multiplying in the body and can ultimately save lives, experts say.

The oral medicines Lagevrio (molnupiravir) and Paxlovid (nirmatrelvir and ritonavir) are effective in treating adults who are at risk of hospitalisation or death.

They are taken in tablet or capsule form early after testing positive to COVID-19 to stop the severity of infection.

"Lagevrio works by interfering with the virus' replication," a spokeswoman for MSD Australia said.

"This prevents the virus from multiplying, keeping virus levels low in the body and therefore reducing the severity of the disease. Lagevrio may protect against severe disease and (help patients) stay out of hospital."

The prescribed pills, which were approved by the Therapeutic Goods Administration in January, have already helped more than 73,000 Australians, according to Health Minister Mark Butler.

They are to be consumed twice daily within five days of the onset of symptoms and cost $6.80 for a concession card holder or around $40 for others.

Common side effects include diarrhoea and nausea.

It comes after the Health Department announced the expansion of the Pharmaceutical Benefits Scheme (PBS) eligibility for treatment, to ease pressure on the healthcare system.

Access will be expanded to Australians over 70 who test positive to the virus, those over 50 with two or more risk factors for severe disease and Aboriginal or Torres Strait Islander people over 30 with two or more risk factors.

People aged 18 or over who are immunocompromised may also be eligible.

Access to the treatment is permitted irrespective of vaccination status.

Australia's COVID-19 death toll has surpassed 10,300 and health authorities are urging people to consider a fourth vaccine dose.

More than 70,000 new infections and 89 deaths have been reported nationwide over the weekend, with Omicron variants BA.4 and BA.5 now the dominant strains of the virus.