Ford's purchase mirrors efforts by U.S. states and cities to buy equipment to store millions of doses of Pfizer's vaccine at temperatures of minus 70 Celsius (minus 94 Fahrenheit), significantly below the standard for vaccines of 2-8 C (36-46 F).

Health care providers and states are preparing for a new type of vaccines by Pfizer and Moderna Inc that require lower temperatures for storage.

"We're doing this so that we can make the vaccine available to our employees on a voluntary basis," Ford spokeswoman Kelli Felker said.

Details of how Ford will use the freezers, which are expected to be delivered by year end, are still being worked out, she said. Ford screens its workers in-plant and, if COVID-19 testing is required, has partnerships with local healthcare providers.

Assembly workers are considered essential in most states, but not at the top of the list for vaccines, which are expected to be distributed first to healthcare workers and nursing home residents.

Automakers have been largely able to avoid spread of the virus among hourly workers in their assembly plants after a two-month shutdown earlier in the year, but COVID-19 cases and hospitalizations are spiking in the United States, especially in the Midwest.

Felker did not know which company is supplying Ford with the freezers. Major manufacturers include Thermo Fisher Scientific Inc, PHC Corp of North America, Luxembourg's B Medical Systems, Stirling Ultracold and Helmer Scientific.

Some specialty freezer makers have warned of months-long waits for units.

Ford, which decided to buy the freezers on its own and is not working with other companies or states, did not disclose how much it spent, but the specialized freezers required by Pfizer's vaccine can cost $5,000 to $15,000 apiece, according to industry officials.

General Motors Co said it had not purchased freezers at this time. "We are taking steps to be prepared to make vaccines available to our employees when the time is right and vaccines are available to us," GM spokesman Patrick Morrissey said.

Fiat Chrysler Automobiles said it is studying the most effective approach to distributing vaccines to employees when they become available.

Officials at Toyota Motor Corp, and the United Auto Workers union, which represents most U.S. hourly workers at the Detroit automakers, did not have an immediate comment.

A Michigan Department of Health spokeswoman said the agency was not aware of companies seeking to buy these freezers. Lynn Sutfin said state officials surveyed healthcare providers and health departments and are aware of about 50 ultra-cold freezers in Michigan. State officials also have purchased another nine, she said.

(Reporting by Ben Klayman; Editing by Jonathan Oatis and Lisa Shumaker)

By Ben Klayman