By Stephanie Stahl

PHILADELPHIA (CBS) — As another holiday weekend approaches, medical experts are concerned with the Delta variant for COVID spreading through Fourth of July crowds.

Fourth of July events in 2020 brought spikes in coronavirus cases, but this year has something new — people vaccinated and protected against the virus that led to the global pandemic that upended billions of lives.

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However, U.S. Surgeon General Dr. Vivek Murthy warns this doesn’t mean all Americans are out of the woods.

“If you are not vaccinated, then you are in trouble,” Dr. Murthy says, adding, “This variant of COVID is highly transmissible, the most transmissible that we’ve seen to date.”

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More than a third of the country remains unvaccinated. The Delta variant is the cause of nearly 26% of current COVID cases. Medical professionals are keeping an eye on the variant and aren’t against extra precautions as needed.

Dr. Peter Hotez, Baylor College of Medicine, told CBS, “I would say right now, if your kids are old enough to wear masks, then they should when they’re indoors, at least until we can get our arms around this Delta variant.”

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When it comes to the holiday weekend, the overall verdict? Medical officials agree the safest way to celebrate is to be outside.

Stephanie Stahl