The BA.5 omicron variant is now the dominant strain in the U.S., and it is leading to a new wave of COVID-19 infections. BA.5 was responsible for nearly 54% of COVID-19 cases in the U.S., and BA.4, a similar variant, accounted for another 17%, according to the latest data from the Centers for Disease Control and Prevention. 

Experts are concerned because this particular variant appears to be good at evading the immune system. 

"This BA.5 variant is hypercontagious, and right behind it, new variants are coming," says Dr. Gregory Poland, an infectious diseases expert and head of Mayo Clinic's Vaccine Research Group. "We will continue to generate these variants until people are masked and immunized." 

Dr. Poland explains that the transmissibility of BA.5 represents the evolution of the virus to become more contagious and able to evade immune protection from previous infection or vaccination. 

"Whether you've been vaccinated, whether you've been previously infected, whether you've been previously infected and vaccinated, you have very little protection against BA.5 in terms of getting infected or having mild to moderate infection," says Dr. Poland. "Thankfully, you still do have good protection against dying, being hospitalized or ending up on a ventilator if you are up to date on your vaccinations." 

Due to the consequences of reinfection, including the possibility of long COVID-19, Dr. Poland urges people to continue to take precautions to protect themselves.

"The reality is, it's important to be up to date on the COVID-19 vaccinations that are recommended for your age group, health condition, etc.," says Dr. Poland. "Sometime this fall, we may well have a variant-focused vaccine, so get it when it becomes available. And wear a proper mask properly when you are indoors around people who are not your family or in a crowded outdoor venue."

On the Mayo Clinic Q&A podcast, Dr. Poland shares the latest COVID-19 news and answers listener questions.