How to Register for Pfizer Vaccine Booster Shots in Mass.

The Baker administration announced details on Friday for how the roughly 600,000 Massachusetts residents who are now eligible for COVID vaccine booster shots can register.

People in the groups approved for a third shot of the Pfizer vaccine -- seniors and and people at risk of COVID because of underlying medical conditions or their job -- can find a location where they can receive the shot at vaxfinder.mass.gov, the administration said.

Anyone unable to use the website can call 211 Monday to Friday between 8:30 a.m. and 6 p.m. and on weekends between 9 a.m. and 2 p.m.

Additionally, officials said that everyone living or working in a long-term care facility in Massachusetts, including the two soldiers' homes, has been prioritized for getting a booster shot -- the Department of Public Health has been planning with facilities and pharmacies to make sure the doses will be delivered on site.

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In a dramatic overruling, the CDC's top official approved the recommendation of booster shots for Americans who have already received 2 doses of the Pfizer vaccine. NBC News medical contributor Dr. Kavita Patel says her practice is ready to administer a 3rd shot to those who want it - between 6 to 9 months after receiving their 2nd dose.

"The Baker-Polito Administration has been working with pharmacies, local boards of health and other health care providers to ensure eligible residents will be able to access the Pfizer booster vaccines at hundreds of locations across the Commonwealth. If you have questions about whether getting the booster is right for you, we encourage you to contact your healthcare provider," Health and Human Services Secretary Marylou Sudders said in a statement.

The state expects to be able to give out more than 300,000 of the booster shots each week by the middle of October, officials said.

More than 4.6 million people across Massachusetts are fully vaccinated -- among the most per capita in the country -- and nearly 99% of Massachusetts seniors have received at least one dose, officials noted.

Booster shots are safe and effective at preventing serious COVID infections, and free, officials noted. They encouraged people with questions to visit mass.gov/covid-19-vaccine for more information.

Federal regulators approved the Pfizer booster shots for certain groups in a process that culminated Friday.