Pfizer Inc is starting a pilot program for COVID-19 immunisation in four US states to help refine the plan for the delivery and deployment of 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 in a statement on Monday.
Pfizer last Monday released initial data on its vaccine developed with German partner BioNTech SE that showed it to be more than 90 per cent effective.
Earlier on Monday, 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.