Americans won't have to pay anything for vaccines that prevent COVID-19.

Zip. Zero. Nada.

That's assuming, of course, that one or more of the vaccine candidates now in development proves effective enough to get the green light from the Food and Drug Administration.

The federal government has committed to purchasing at least 100 million doses each from a number of drugmakers, among them Novavax (NVAX -7.42%), Moderna (MRNA -0.15%), and Johnson & Johnson (JNJ -0.47%), as well as Pfizer (PFE 0.88%) and BioNTech (BNTX -1.05%) which are working on a vaccine program together. Most of those agreements would allow the U.S. government to purchase additional doses beyond their initial commitments.

Gloved hands giving an injection into a shoulder

Image source: Getty Images.

Paul Mango, deputy chief of staff for policy at the Department of Health and Human Services, said the government will cover the cost of administering the vaccines for patients enrolled in Medicare and Medicaid, according to an article in The Wall Street Journal.

The agency is working with healthcare companies to distribute the vaccines when and if they're ready, and is also working with the insurers to makes sure their members aren't charged copays for the vaccine.

A federal fund created by the CARES Act will cover the cost of the vaccines for individuals who don't have any government or commercial insurance.

The supply of vaccine will likely be constrained initially, considering that there are more than 328 million people in the U.S. and most of the COVID-19 vaccine candidates being developed have two-dose regimens. The government will prioritize the inoculation of healthcare workers, senior citizens, residents of nursing homes, and others at high-risk, according to the Journal article.