Just hours after federal officials recommended booster shots of the Pfizer COVID-19 vaccine for millions of Americans, a steady stream of patients lined up at pharmacies to get their dose.”I’m 66 and I want to make sure I’m safe,” said Ellyn Penn, who got her shot Friday at Union Pharmacy in Newton.In Massachusetts, state officials said approximately 600,000 people will be eligible for these booster shots immediately, based on the federal eligibility guidelines. People 65 and older, nursing home residents and those ages 50 and up who have chronic health problems such as diabetes should be offered a booster once they’re six months past their last Pfizer dose, CDC Director Dr. Rochelle Walensky ruled late Thursday.And a broad swath of other adults can decide for themselves if they want a booster once they reach that six-month mark: Younger people with underlying health problems — plus people at increased risk of infection because of their jobs, such as health workers, or their living conditions, such as jails or homeless shelters.”The issue isn’t that we’re getting sick and ending up in the hospital, we’re not,” said Dr. Shira Doron, an epidemiologist at Tufts Medical Center. “But we are getting sick and going out of work for ten days at a time when we can’t afford to lose anybody because the hospital are full.” “I”m over 65 and I got the other vaccinations in January and February, so that’s close to eight months ago,” said Karen Gould, who also got her booster Friday. Rhode Island-based CVS said in a statement its pharmacy and MinuteClinic locations that offer the Pfizer vaccine would be ready to begin administering the booster shots by late Friday.”We strongly encourage customers to schedule an appointment in advance at CVS.com to ensure they are able to access the correct vaccine at a convenient time and location,” CVS spokesperson Matt Blanchette said.Illinois-based Walgreens said its locations would also begin administering the shots Friday.”Walgreens has played a vital role in responding to COVID-19 as millions have turned to us as a convenient vaccination destination and critical point of community care,” Walgreens President John Standley said in a statement. “In addition to providing booster shots, our pharmacy teams remain readily available to advise patients, address questions and co-administer flu and COVID-19 primary vaccines to help protect our communities.”Additionally, Massachusetts’ Vaxfinder online directory will host a list of hundreds of locations where boosters are available.