Dr. Anthony Fauci is emphatically calling on people to get their COVID-19 vaccine booster shots, even if they're considered "fully vaccinated" without it. "We are telling everybody, and I will state it very clearly now, that optimum protection is with a boost," Fauci said Thursday in an interview on CBSN. "If you are not boosted, get boosted. What is called by definition, for legal or other purposes, a 'fully vaccinated person,' is, in fact, irrelevant. If you want to be fully protected, get boosted. I am saying it very loud and very clear right now." The Centers for Disease Control and Prevention recommends a booster six months after getting the second dose of Pfizer or Moderna's vaccine, or two months after the single-dose Johnson & Johnson shot. "This is a very dynamic situation," Fauci said. "We are dealing with a brand-new, extraordinarily transmissible variant, the Omicron variant." Fauci said even though COVID-19 cases are again on the rise, the vaccines are doing their job by protecting people against more severe illness. "Although the vaccination, when you have a highly transmissible virus, may not prevent you from getting infected, it is very likely that you will either be without symptoms or minimally symptomatic. The major purpose of the vaccine is to prevent you from getting sick, from getting clinically ill and, hopefully, to prevent you from getting hospitalized and dying," Fauci said. "In fact, the data show that the vaccines are highly successful in doing just that." For New Year's celebrations this weekend, Fauci urged potential revelers to make educated decisions. "Family gatherings, people who are together who know that they are vaccinated and boosted, in a setting of the home, is fine," Fauci said. "But I think it would be prudent for people, as best as you possibly can, to avoid these types of 30-, 40-, 50-person parties, where you don't know the vaccination status of the people that are surrounding you. This is a very formidable virus." Fauci also had a message for those who have not gotten vaccinated. "If you look at the comparison between people in the hospital who die, who were vaccinated versus unvaccinated, overwhelmingly multi-multi-fold greater likelihood of getting into trouble if you are unvaccinated. Point number one," Fauci said. "Point number two: If you are not getting vaccinated because you think it's not safe, there have been billions of vaccinations given worldwide. It is very safe." "So what is the reason why you do not want to get vaccinated?" Fauci asked. "Is that because it is ideological? Or a political reason not to do it? That doesn't make any sense when you're dealing with a crisis that this nation and that this world is in right now. So hopefully, when people at least look at the facts of what's going on, they will realize that not only to protect themselves and their family, but their communal responsibility, to be able to be part of a nationwide effort to contain the outbreak. As opposed to being people who don't want to have anything to do with helping the country get out of this crisis."