Eighteen states in the US and some major-label businesses have announced plans to end Covid-19 mask mandates either immediately or in the weeks to come, but others such as California, New York and New Jersey are moving forward with caution.

Many Americans went mask-less in public on Friday for the first time in months, a day after the Centers for Disease Control and Prevention (CDC) relaxed its guidelines on face coverings for people who have been fully vaccinated against Covid-19, reports Xinhua news agency.

The changes came as more than one third of Americans are fully vaccinated, and the daily number of new cases slipped below 35,000, the lowest since September 2020.

Businesses large and small are also grappling with how to adapt to the CDC's surprise guidance.

Some of the nation's largest retailers said that they have no immediate plans to change their policies and would continue requiring both customers and workers to wear masks on the premises, according to local media reports.

Other businesses said they are re-evaluating their protocols.

Walt Disney World located in Orlando, Florida announced on Friday that masks and face coverings for guests would be "optional in outdoor common areas" at the resort starting on Saturday.

Grocery chain Trader Joe's became the first prominent US retailer on Friday to drop its mask policies for vaccinated shoppers.

It was followed by Walmart, the country's No. 1 retailer with more than 4,700 stores, which said in a memo to employees that vaccinated customers can shop without masks.

Fully vaccinated employees will be able to work without masks as of May 18, although workers who haven't been fully vaccinated will still need to wear masks.

The company also said it is giving $75 of bonuses to vaccinated workers as "a thank you for getting vaccinated", but employees will need to provide a proof of inoculation to get the money.

"While progress against the pandemic is being made, Americans eager to enjoy spring weather are receiving mixed messages about masking," CBS News said in a report on Saturday.

"What the CDC released are just guidelines on mask wearing, leaving it up to states, stores, sports venues and the rest to decide if masks are required.

"What the US is now seeing mirrors what we've seen throughout the pandemic: a patchwork of rules that vary from place to place," it added.

Whatever the decision, one thing is clear, the CDC's new guidelines specifically apply to vaccinated people.

CDC Director Rochelle Walensky said this week that people who are not vaccinated should not be taking off their masks.