But new rules announced by the state government on Monday that aim to ease the crisis to critical supply chains could get staff back to work sooner.

The impact of the spread of COVID has taken a huge toll on businesses across the region with many struggling to stay open with staff subject to isolation requirements.

General manager Dean McKenna said the staff shortages had affected Midfield's production line with many of them deemed close contacts who were having to isolate.

But truck drivers and contractors have also impacted.

"Today we are operating at about 25 per cent of what we should be doing," Mr McKenna said on Monday.

"There's truck drivers out, contractors out and production, we just can't get through the lines."

He said he was hopeful that things would improve but that depended on whether Victoria fell into line with New South Wales and allowed people to go back to work sooner.

Mr McKenna said the rule that people needed to isolate for seven days "knocked whole households out" with many of the workers living with each other.

However, he said it would not have a major impact on the company's supply chain for Warrnambool saying it would eventually catch up.

"Generally it will across industry because industry is in similar situation everywhere," he said.

Chief medical officer Professor Paul Kelly said major supermarkets such as Woolworths and Coles had reported an absenteeism rate of 30 to 50 per cent, particularly in its distribution centres.

"It's huge," Mr Kelly said. "They cannot operate in those circumstances. We need to move fast to make these risk-based approaches to deal with that issue."

Prime Minister Scott Morrison described the arrival of the Omicron variant as a "gear change" and "we have to push through".

To ensure Victorians can continue to access essential food supplies, workers in the manufacturing, distribution or packaging of food and beverages including retail supermarket workers may be exempted from close contact isolation requirements in order to attend work, the Victorian Government announced on Monday.

The rule comes into effect from 11.59pm on Wednesday but applies only if it is necessary for continuity of operations and other options have been exhausted.

To mitigate risks, exempted workers must be asymptomatic, undertake daily RATs for 5 days and return a negative result prior to attending work.

They can't enter shared break areas, and employers are asked to facilitate solo break time.

In addition, face coverings must be worn, using N95/P2 respirators if possible. Both the worker and workplace must consent to the worker's return.

The new close contact isolation exemption for asymptomatic food distribution workers is similar to the arrangements already in place for critical healthcare workers.

Health Minister Martin Foley also announced mandates for a third dose of the vaccine for some essential workers including those in abattoirs.

"The abattoir, meat, poultry and seafood processing workers - all of these groups are already covered by existing mandates for those first two vaccinations. And this is a sensible addition for the relatively high-risk nature that these sectors operate when it comes to vaccine protection," he said.

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