RELATED: Dr. Fauci Warns Vaccinated People Not to Do This When Gathering. During a National Institutes of Health (NIH) lecture on Jan. 4, Anthony Fauci, MD, top White House COVID adviser and director of the National Institute of Allergy and Infectious Diseases (NIAID) for the NIH, discussed the changing virus and how it is affecting vaccinated people. According to Fauci, there is evolving language around what it means to be fully vaccinated against COVID now that the Omicron variant is circulating. “We’re using the terminology now ‘keeping your vaccinations up to date,’ rather than what ‘fully vaccinated’ means,” Fauci said. “Right now, optimal protection is with a third shot of an mRNA or a second shot of a J&J.” All three vaccine manufacturers have said their boosters increase protection against the new variant. According to early research, Pfizer’s booster provides a 25-fold increase in neutralizing antibodies against Omicron, Moderna’s produces a 37-fold increase, and two doses of Johnson & Johnson’s vaccine has cut hospitalizations in South Africa—where Omicron was first dominant—by 85 percent. Despite virus experts and manufacturers touting boosters as the optimal protection against the Omicron variant, only 34 percent of fully vaccinated people eligible for an additional shot in the U.S. have gotten it so far, according to the CDC. The CDC has yet to change its definition of fully vaccinated, however. According to the agency’s most recent guidelines, which were updated on Jan. 5, “everyone 5 years and older is recommended to receive a primary series of a COVID-19 vaccine to be considered fully vaccinated.” A primary series does not currently include a booster shot, per the CDC. “In terms of the definition of ‘fully vaccinated,’ as you know, the definition right now is two doses of an mRNA vaccine or a single dose of the J&J vaccine,’” CDC Director Rochelle Walensky, MD, said during a White House briefing on Dec. 15. “We are continuing to follow that science and it is literally evolving daily. And as that science evolves, we will continue to review the data and update our recommendations as necessary.” RELATED: For more up-to-date information, sign up for our daily newsletter. Nevertheless, the agency has made major moves recently to acknowledge the importance of booster shots. On Jan. 4, the CDC recommended that third shots of the Pfizer vaccine be administered starting five months after the second dose, which is shorter than the original six-month timeline that the agency recommended when first endorsing booster shots. And on Dec. 27, the agency updated its quarantine and isolation guidelines, noting that individuals aged 18 or older who have come into close contact with someone who has COVID no longer need to quarantine if they have received all recommended vaccine doses, include boosters. If you haven’t gotten this additional shot, the CDC says you should stay home and away from other people for at least five days after your last contact with an infected person.ae0fcc31ae342fd3a1346ebb1f342fcb “Our CDC guidance has been very clear that people should get their boost when they are eligible. That is both because of waning immunity and because we need more protection against Omicron,” Walensky said during a Dec. 29 White House press briefing. When it comes to people who have only gotten their first or second doses of the COVID vaccine, she added, “We do know that they do have some protection against severe disease and death but that they do have quite a bit of waning with regard to protection against infection. And since these are guidelines for quarantine, we really wanted to have those measures in place since they have had quite a bit of waning protection against infection.” RELATED: If You Don’t Have a Booster, You’ll Be Barred From This, as of Jan. 17.