READ THIS NEXT: Boosters Won’t Protect You Against Omicron If You’ve Done This, Study Finds. Everyone 12 years and older is eligible for at least three COVID vaccine doses: a primary two-vaccine series and a booster. But some people already have the green light for a fourth dose. In March, both the CDC and the U.S. Food and Drug Administration (FDA) authorized a second COVID booster for certain immunocompromised individuals, as well as anyone age 50 or older who got their first booster at least four months ago. At the time, the agencies only advised that boosted people in these groups could consider getting a fourth vaccine dose. But in May, the CDC updated its guidance to recommend that those eligible for a second booster should get the additional shot now. “With cases increasing, it is important that all people have the protection they need,” CDC Director Rochelle Walensky, MD, said in a May 19 statement. This might seem like a small distinction to some, but many virus experts are now warning that it isn’t. George Diaz, MD, the division chief of medicine at Providence Regional Medical Center Everett in Everett, Washington, told Tulsa World that without a second booster, some boosted individuals likely don’t have “much protection” against COVID anymore. “Right now, what we’re seeing is that usually about four months after a booster you start seeing significant waning of effectiveness,” Diaz explained. “And by about 150 days, you may actually not have much protection at all.” The CDC’s latest data indicates that of the more than 213 million fully vaccinated individuals eligible for their first booster, only 47 percent have gotten the shot. But the rate for the second booster is even lower. The agency reports that only 24 percent of those who are eligible for the second booster based on their age have gotten an additional dose. RELATED: For more up-to-date information, sign up for our daily newsletter. According to Diaz, one of the issues making booster rates so low is that some people become overconfident once they’ve had at least two shots. “They think they should be fine, and that’s not the case. Vaccine effectiveness wanes over time,” he warned. Another major problem is that some people are confused about what additional doses of the existing COVID vaccines are protecting people from, as more and more vaccinated and boosted people are getting breakthrough infections, according to Aaron Wendelboe, PhD, an epidemiologist and associate professor at the University of Oklahoma College of Public Health. But if you look at the protection against severe COVID, “the boosters do work,” Diaz said. “One thing to keep in mind is when we talk about ’effective against,’ sometimes we’re talking about effectiveness against infection, hospitalization and death. And the main point is that these boosters are effective at preventing hospitalization and death,” Wendelboe explained to Tulsa World. “So some people will say, ‘I might still get infected.’ Well, that might be true, but it’ll keep you out of the hospital, especially if you’re in those higher risk vulnerable groups.“ae0fcc31ae342fd3a1346ebb1f342fcb In May, the CDC said it was strengthening its recommendation for the fourth COVID shot because the country was seeing “a steep and substantial increase in hospitalizations for older Americans,” The New York Times reported. According to the agency, most Americans 50 and older have gone more than six months without a COVID vaccine dose at this point in the pandemic. This has left “many who are vulnerable without the protection they may need to prevent severe disease, hospitalization and death,” the CDC said. So whether you’ve been waiting to get another COVID shot or you’ve just forgotten about it altogether, you need to get your additional booster if it’s been four months since your first boost and you’re eligible for the second. “Unless your health care provider recommends otherwise, it’s really recommended that you go and get that (second booster),” Wendelboe confirmed. READ THIS NEXT: Virus Experts Just Gave This Pressing New Warning to Boosted People.