BOSTON (CBS) – Great Britain became the first country in the West to approve a COVID-19 vaccine for public use Wednesday and a local expert says the U.S. isn’t far behind.

Dr. Ashish Jha, the Dean of Brown University’s School of Public Health, said the Food and Drug Administration is only a few days behind the U.K. in the rollout of a vaccine from Pfizer.

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“I think our FDA has been working really fast as well and I expect to have an authorization next week,” he told CBS This Morning.

Once the FDA approves emergency use of Pfizer’s coronavirus vaccine, the agency is then expected to approve one from Cambridge-based Moderna.

Health care workers and the elderly will be the first to receive a vaccine in the next few weeks. Massachusetts Gov. Charlie Baker said it will likely be available to the general public next spring.

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“There are going to be two doses that everybody needs to get. You may get a little bit of protection after the first one, but it’s really the second dose that makes the big difference and we think you have protection relatively soon thereafter, probably within a week or two after that,” Dr. Jha told CBS.

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“How long it lasts we don’t know. My hope is it lasts at least a year but, obviously we haven’t done those longer term studies yet, so we’re not sure.”

Once vaccines are available, Dr. Jha said there will be a massive production to get them out.

“This is probably the most complex immunization effort our country has ever undertaken. It’s very complicated because we’re going to have multiple vaccines, multiple groups to get vaccinated, tracking to make sure everybody’s getting their second dose. It’s really complicated,” he said.

“Do I think we can pull it off? I do. We’re going to need an effective federal government, we’re going to need state governments to act effectively and then we’re going to have to work very closely with pharmacies and doctors’ offices. It’s going to take a lot of work. I think we’re up for the task, but we’ve got to pay close attention to all of it.”

Until people are vaccinated, Dr. Jha said how you behave in the pandemic still matters.

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“We are absolutely not out of the woods. In fact, we’re probably in the darkest days of the pandemic. The next six weeks, while the vaccines are starting to roll out, are going to be very, very hard, lots of infections, lots of hospitalizations, unfortunately lots of deaths. I tell people, anybody who gets infected now and dies, is somebody who would have gotten a vaccine 2-3 months from now. So we really, really need to watch our behavior to protect people until we get to vaccinations.”