For Americans who have not yet received a flu vaccination, it's not too late, according to Dr. David Samadi, chairman of Urology and Chief of Robotic Surgery at Lenox Hill Hospital in New York City.
Samadi told "The Steve Malzberg Show" on Newsmax TV that it is still important to get the vaccine to lessen the chance of getting a full-blown bug.
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Still, no vaccine is perfect, he noted.
"When it comes to flu, unfortunately, the bug itself is smarter than us. So every year it starts to change their shape, their mutations. They kind of change the way they look," Samadi said.
"And so we have to kind of modify our vaccine, kind of always chasing them to make sure that we get it right … That's part of the reason why we're not hitting the target every year."
He said that scientists are always working on ways to improve the effectiveness of vaccines, including one attacking four different strains of flu.
"Hopefully, with the new vaccine that covers four bugs, we'll be much better off," he said.
"But, again, just a message to a lot of people, if you have not been vaccinated, you have to."
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