South Australia has eased eligibility rules to access the vaccine for the Japanese encephalitis virus even though there have been no confirmed cases across the state this year.

The change removes the requirement to be outdoors for four hours on most days for those people living or engaging in flood recovery and clean-up efforts along the River Murray.

It also includes people experiencing homelessness or living in conditions with limited mosquito protection such as tents or caravans and brings SA into line with Victoria and NSW.

Since a targeted encephalitis vaccination program began in October last year, SA has administered about 23,800 doses with a further 9000 available to people living and working in Riverland communities.

There were two deaths among nine confirmed cases of the virus in the state last year. There have been no cases reported so far in 2023.

SA Chief Public Health Officer Professor Nicola Spurrier said the vaccine provided lasting protection for most people.

"So it's important for eligible people to take up the vaccine now whilst available in order to protect themselves against the virus in the warmer months when mosquito activity increases," she said.

"I strongly encourage eligible people in the River Murray, Coorong and surrounding areas to get vaccinated against JEV if they have not already done so."