Two of eight new COVID-19 cases in South Australia are suspected to be the Omicron variant, health officials say.

SA Health reported the eight cases on Friday with four infections in interstate travellers, three locally-acquired and one in someone who recently returned from overseas.

"Two of today's interstate cases are suspected to be the Omicron variant," SA Health said in a statement.

Earlier, Premier Steven Marshall said tests were underway to determine if the new strain had been found in SA.

"We don't have any confirmation so we're taking it very cautiously," Mr Marshall told radio FIVEaa.

"It hasn't moved as quickly as we were thinking it might but we still have very little information on Omicron.

"Sometimes when you get a new case it takes some time to get that assessment, I think they call the genome sequencing, so we can know exactly what strain it is.

"We did get a couple of cases overnight and we are testing those to see if they could be our first cases of Omicron."

It remains unclear if the possible spread of the new strain to SA could disrupt plans to lift more local virus restrictions later this month or early in January based on the vaccination rate hitting 90 per cent.

On Thursday Mr Marshall said the government just needed a "few more days" before it made the call based on the number of people lining up for their second jab.

"We just need a few more days to see what that run rate is going to be in South Australia," he told reporters.

"The race is on at the moment to get to 90 per cent of all those 12 and over and I'm hopeful that we can do that by the end of the year."

The most recent SA Health forecast suggests the double-dose target would be reached between December 23 and January 3.

Among the measures that could be revised are density limits at various venues, restrictions on dancing in nightclubs, and the 150-person cap on private functions.

SA now has 53 active coronavirus infections with two people in hospital in a stable condition.

The other cases are being managed in hotel quarantine.

Also on Friday, a deadline for public transport workers to be vaccinated was pushed out from December 20 to the new year.

Workers must now have a first jab and evidence of a booking for a second dose by January 3.