Pfizer is starting a pilot program for COVID-19 immunisation in four US states to help refine the plan for delivering and deploying its vaccine candidate.

The US drugmaker said it had selected Rhode Island, Texas, New Mexico and Tennessee for the program because of their differences in overall size, diversity of populations and immunisation infrastructure, as well as the states’ need to reach individuals in varied urban and rural settings.

“The four states included in this pilot program will not receive vaccine doses earlier than other states by virtue of this pilot, nor will they receive any differential consideration,” Pfizer said on Monday.

The trials come as coronavirus cases across the US top 11 million and with more than 1000 American deaths from the virus every day.

Hospital admissions have also reached record levels with nearly 150,000 new cases across the US on Monday.

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Michigan, Washington and California are among the latest American states to bring in strict regulations to try to halt the spread of the virus.

There are restrictions on on-site teaching, indoor dining, gyms, cinemas, theatres and museums.

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Last Monday, Pfizer released initial data on its vaccine developed with German partner BioNTech SE that showed it to be more than 90 per cent effective.

This week, rival Moderna Inc said its experimental vaccine was 94.5 per cent effective in preventing COVID-19 based on interim data from a late-stage trial, boosting hopes that vaccines against the disease may be ready for use soon.

Both the Pfizer and Moderna vaccines use a new technology called synthetic messenger RNA to activate the immune system against the virus.

Experts have raised concerns about the distribution challenges associated with Pfizer’s vaccine due to its specialised storage requirements.

-with AAP