OKLAHOMA CITY (KFOR) – Medical officials have hoped since the start of the COVID-19 pandemic that the nation would achieve herd immunity, but a top Oklahoma doctor said the Delta variant may have put herd immunity out of reach.

Herd immunity is reached when a large portion of a community becomes immune to an infectious disease, making it unlikely that the virus will spread from person to person. At such a juncture, the entire community is protected, not just individuals who are immune, according to the Mayo Clinic.

Dr. Dale Bratzler, OU Health’s Chief COVID-19 Officer, spoke during Tuesday’s Healthier Oklahoma Coalition meeting, and said that the highly-contagious Delta variant, which has spread across the globe like wildfire, is much more contagious than the original Alpha variant.

Bratzler said herd immunity might have been achieved with Alpha as the primary variant with about 60 to 65 percent of the population having been vaccinated or having had the virus.

However, the rate of infection is much higher with the Delta variant.

“That’s because if you’re infected with the Delta variant and we measure the viral load – how much virus is actually in your airways – that number’s 1,000 to 1,200 times higher than it was with the Alpha variant,” Bratzler said.

Bratzler warns because of Delta’s higher viral load, even the vaccinated can get COVID.

But Bratzler also gave some reassurance, saying the vaccinated do not get nearly as sick with the Delta variant as those who have not had the shot.

Bratzler and other Oklahoma medical officials urge Oklahomans age 12 and up to get the COVID-19 vaccine.