Lifestyle Health CDC Warns Rapid Spread of Omicron Could Lead to Massive Spike in COVID Cases by January Dr. Anthony Fauci said, though, that booster shots should be enough to prevent infections By Julie Mazziotta Julie Mazziotta Twitter Julie Mazziotta is the Sports Editor at PEOPLE, covering everything from the NFL to tennis to Simone Biles and Tom Brady. She was previously an Associate Editor for the Health vertical for six years, and prior to joining PEOPLE worked at Health Magazine. When not covering professional athletes, Julie spends her time as a (very) amateur athlete, training for marathons, long bike trips and hikes. People Editorial Guidelines Published on December 15, 2021 02:42 PM Share Tweet Pin Email Testing for COVID-19. Photo: PAUL RATJE/AFP via Getty The Centers for Disease Control is warning of another major winter spike in COVID-19 cases as the highly contagious omicron variant begins its rapid spread around the U.S. In a briefing with leaders from major health organizations on Tuesday morning, CDC officials said that in the two weeks since omicron was first identified in the U.S. the variant has moved quickly, with cases containing omicron jumping up sevenfold in one week. The CDC said omicron's rapid rise could lead to a "triple whammy" — a high number of new infections coinciding with the severe cases from the older delta variant, with both bringing down already-overwhelmed hospital systems. "I'm a lot more alarmed. I'm worried," Marcus Plescia, chief medical officer for the Association of State and Territorial Health Officials, said after attending the briefing, according to The Washington Post. The CDC had said at the briefing that "we got to get people ready for this," he said. Omicron Appears to Cause Less Severe Illness but Is More Resistant to Pfizer Vaccine That is the worst-case scenario based on data modeling from health experts, the CDC said. In another model, omicron had a slower spread with a surge in the spring. The U.S. had a reported 116,892 new cases on Tuesday, an increase of 46% over the last two weeks, according to The New York Times. Hospitalizations have also jumped up 22% during that time span, and average around 67,000 a day. RELATED VIDEO: Here are Some Myth-Busting Facts About COVID-19 Vaccines How quickly omicron will spread, how severe it is and if vaccines will work against the variant are all still fairly unknown questions in the first month since it was identified. The first major, real-world study of patients infected with omicron was released Monday, and found that it mostly led to mild illnesses, but that two doses of Pfizer's COVID-19 vaccine prevented infection only 30% of the time. Top infectious disease expert Dr. Anthony Fauci said Wednesday, though, that a third, booster dose should provide strong protection against infection. He urged people to get vaccinated if they haven't yet, and for those who received two doses of the Moderna or Pfizer vaccines more than six months ago to immediately get a booster dose. Fauci also said that the pharmachutical companies will likely not need to formulate an omicron-specific booster dose. 5 Things to Know About COVID Booster Shots, According to an Infectious Disease Doctor "Our booster vaccine regimens work against omicron," Fauci said, according to The New York Times. "At this point, there is no need for a very specific booster. And so the message remains clear: If you are unvaccinated get vaccinated, and particularly in the arena of omicron if you are fully vaccinated, get your booster shot."