Pfizer COVID-19 booster shots are now available to anyone 65 or older or at high risk of the coronavirus, as long as they were fully vaccinated at least 6 months ago — a number in the millions.Many wonder if Pfizer’s booster is the same dose as the previous vaccines in its two-dose schedule, or if it is smaller than those doses.Dr. Mark Siedner, an epidemiologist within the Division of Infectious Diseases at Massachusetts General Hospital, says the amount of vaccine in the Pfizer COVID-19 booster is exactly the same as the company’s prior shots.”(It’s) the 30 microgram dose, which actually makes implementation of the booster rollout much easier for us,” Siedner said.There are also concerns that the side effects from the booster shot could be more common, and potentially more serious, than the second dose of the COVID-19 vaccine.Siedner says the best data on booster shots come from Israel, which has administered boosters to hundreds of thousands of people since July.”They’ve surveyed people after the booster shot and the vast majority say that the third shot was just like the second, maybe some evidence that it’s actually slightly better tolerated,” he said. “But they’ve really had no increased rates of severe adverse events, so I think people can assume that the third shot, if anything, will be very similar to the second shot.”With flu season approaching, many are also wondering if it is safe to receive a flu shot and the COVID-19 booster shot at the same time.”So now we know these vaccines extremely well. They’re very safe. They’re well-tolerated,” Siedner said. “And so we are now recommending if you’re due for your influenza shot and your COVID-19 booster at the same time, go ahead (and) get two birds for one stone. They’re safe. They do not cross-react and it’s safe to get them both on the same day.”One viewer asked WCVB whether her 74-year-old husband, who has COPD and received both doses of the Moderna COVID-19 vaccine, is safe to get the Pfizer booster shot.Siedner says Moderna has also submitted data to the U.S. Food and Drug administration about approval for its COVID-19 booster shot, and that the FDA and U.S. Centers for Disease Control and Prevention could review and approve Moderna’s booster within the next few weeks.”For those who got the Moderna vaccine, myself included, it’s a little too early right now for the booster. They haven’t yet been improved,” he said. “But I think people should realize the data on the Moderna vaccine and the Johnson & Johnson vaccine remain quite strong. These vaccines have extremely strong protection against hospitalization, against death. So while we’re waiting for more data about these booster shots and other vaccines, I think we should all take comfort in the fact that these vaccines continue to work extremely well and they’re doing their job.”