Defeating this pandemic and the highly contagious Delta variant isn't just about protecting yourself through vaccination -- it's also about having others in the community vaccinated, doctors say.
"Even if you are vaccinated, if you're living in an area with high rates of Covid-19 spread -- and with the Delta variant surging -- there is a chance that you could become infected," said emergency physician Dr. Leana Wen, visiting professor at George Washington University's Milken Institute School of Public Health.
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The Delta strain is the most transmissible coronavirus variant identified so far, the head of the World Health Organization said. It's about 40% to 60% more transmissible than the highly contagious Alpha (B.1.1.7) variant, according to the European Centre for Disease Prevention and Control.
In the United States, the Delta variant has spread to every state and is now responsible for more than 50% of Covid-19 cases, the US Centers for Disease Control and Prevention said.
"In some parts of the country, this percentage is even higher, especially in areas with low vaccination rates," the CDC said. "This rapid rise is concerning and threatens the progress the United States has made toward ending the pandemic."
As the Delta variant keeps spreading, "we know that there is a risk of breakthrough infection" among fully vaccinated people, Wen said. "So even if you are vaccinated, you could still get infected. The safest thing is for everyone around you -- even if you are vaccinated -- to also be vaccinated as well."
But even when people do get breakthrough infections, the vaccines are still "very, very high in effectiveness" when it comes to preventing severe illness or hospitalization -- well into the 90% range, said Dr Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases.
There are some doctors who have expressed interest in giving a booster dose of vaccine to some patients, such as those who might be immunocompromised, Fauci said Sunday.
But the CDC and the US Food and Drug Administration say those who are fully vaccinated don't need a booster shot right now.
"There will always be people, well-meaning people and well-meaning companies will say, 'You know, the way we look at the situation, it looks like you might need a booster, so let's go ahead and give a booster.' But that's not a formal recommendation," Fauci said.
"Data evolves. You get more information as the time goes by. So when you get to the point where you have enough information to make a firm recommendation, that is not flip-flopping. That is making recommendations as the data evolve."