"The reason we have the COVID-19 delta variant, the reason we have the delta plus variant is because of unimmunized people who get infected," says Dr. Gregory Poland, an infectious diseases expert and head of Mayo Clinic's Vaccine Research Group. He adds that 99.2% of the recorded COVID-19 deaths in the U.S. are in people not vaccinated against the virus.

This is why he cautions folks who may be traveling this Fourth of July holiday and throughout the summer.

"You don't know what variants people are carrying, how symptomatic they are, the health of their immune system, or if they've been vaccinated," says Dr. Poland. "When you are around groups of people indoors that are not in your bubble, so to speak, I think you should still wear a proper mask."

In this Mayo Clinic Q&A podcast, Dr. Poland explains why, even if you are fully vaccinated for COVID-19, you should still consider being masked in some situations. He also discusses breakthrough infections in certain subpopulations, and what that may mean for needing booster shots. And he talks about parasomnia.
Research disclosures for Dr. Gregory Poland.