According to the CDC, you're fully vaccinated two weeks after you receive your second dose of the Moderna or Pfizer vaccine, or two weeks after a single dose of Johnson & Johnson's vaccine.

The CDC also considers you fully vaccinated if you received any single-dose vaccine listed for emergency use by the World Health Organization or any combination of the two-dose vaccines approved by the FDA or listed by the WHO for emergency use.

Though that official definition of "fully vaccinated" isn't likely to change, the CDC website replaced the term "fully vaccinated," meaning maximally protected, with the more general descriptor "up to date."

White House medical adviser Dr. Anthony Fauci has said three shots should be considered the new baseline -- part of the primary series of vaccinations rather than a "booster."

Fauci said his team has moved away from using "fully vaccinated" altogether, in favor of  the phrase "keeping your vaccinations up to date."  

"Right now, optimal protection is with a third shot of an mRNA or a second shot of a J&J," Fauci said at a National Institutes of Health presentation in early January. 

Experts say the CDC's definition of 'fully vaccinated' needs to include booster shots

As preliminary studies show omicron's ability to infect those who only received an initial series of shots, medical experts say the terminology needs to change.

In an op-ed in The Hill, Dr. Dorry Segev, professor of epidemiology at Johns Hopkins Bloomberg School of Public Health, said the year-old standard of the primary two shots of an mRNA vaccine or one of Johnson & Johnson's "has not aged well."

Five months after being "fully vaccinated," as defined by the CDC, "our antibody levels have likely dropped substantially, and with them, our first line of defense against acquiring and replicating -- and thus shedding and spreading -- the virus."

Segev urged the agency to add booster shots to its definition of fully vaccinated.

"If it [was] important to distinguish between vaccinated and unvaccinated when CDC first established this definition, now it is similarly important to distinguish between boosted and unboosted," he wrote. "To put it more bluntly, someone whose last dose of the SARS-CoV-2 vaccine was over five months ago should no longer be considered 'fully vaccinated' and is likely no longer protected enough to be around strangers indoors."

Changing the terminology will encourage some vaccine-hesitant or "booster-hesitant" Americans, Segev added.

How many shots to be protected from omicron?

Why do I need a booster shot anyway?

Mounting evidence shows COVID vaccine protection decreases over time and that booster shots are needed to "top up" COVID-19-fighting antibodies, especially against omicron. Several studies indicate, for example, that Pfizer's vaccine begins to wane after just two or three months.   

The US Food and Drug Administration expanded the authorization of boosters to include everyone 12 and older at least five months after receiving a second dose of the mRNA vaccines, or two months after receiving the Johnson & Johnson vaccine.

Breakthrough cases of COVID-19 in people who've completed their initial vaccinations have risen notably with omicron. 

Will 3 vaccine doses become standard? 4?

Although the definition for fully vaccinated hasn't changed, three doses has become the de facto standard for many. "Although two doses of the vaccine may still offer protection against severe disease caused by the omicron strain, it's clear from these preliminary data that protection is improved with a third dose of our vaccine," Pfizer Chairman Albert Bourla said in a statement on early results of the Pfizer vaccine's continued effectiveness.

Will there be a fourth shot? Israel has already started rolling out a fourth vaccine shot for medical workers, people 60 years or older and people who are immunocompromised. The country recently began a study on the effectiveness of a second booster, testing 154 health care workers at the Sheba Medical Center. The Israeli newspaper Haaretz reports that a fourth vaccine dose seems as safe as the third dose and increases vaccine protection fivefold.

At a National Institutes of Health presentation, Fauci stressed the importance of first collecting and analyzing data from the third shot before considering a fourth dose: "I would say that we need to find out what the durability of protection of the third shot is before we start thinking about the fourth shot."

Which places are requiring booster shots?

Many schools, businesses, and countries are mandating booster shots: Apple now requires all store and corporate employees to be boosted, and Puerto Rico has enacted booster shot requirements for all public school students 12 and older, as well as all residents working in tourism or entertainment, according to AP. 

Starting Monday, Jan. 24, per Maui Now, people in Maui, Hawaii, must be "up to date" with boosters to enter restaurants, bars and gyms. Spain also recently declared that all visitors to the country must be boosted if it's been 270 days since their initial vaccination, joining France, Croatia, Israel, and the Netherlands in the group of countries now requiring boosters.

Last fall, Connecticut's Wesleyan University became the first college to make boosters mandatory for students. Many other colleges followed suit, including all of the Ivy League schools. More colleges and universities are announcing booster requirements every week. The website University Business currently lists 331 colleges that require booster shots for students and staff.

Will we need an omicron-specific booster to guard against the virus?

If two doses of the Moderna or Pfizer COVID-19 vaccine are not enough to guard against omicron, would we need a variant-specific booster to restore protection? According to Fauci, "At this point, there is no need for a variant-specific booster."

But getting people to upgrade from two doses to three will take additional effort: The CDC website says more than 210 million Americans right now are "fully vaccinated" with the Moderna, Pfizer or Johnson & Johnson vaccines. That's 63.3% of the total US population. However, only 83.5 million in the US have received a booster -- 39.7% of the so-called fully vaccinated, or a little more than 25% of the total US population. 

Moderna has said it is studying an omicron-specific vaccine, as well as a multivalent shot that could protect against the alpha and delta strains, PTS Terbaik ASEAN but clinical trials aren't expected to start until next year. 

When can I get a booster shot?

The CDC says you can "ensure you are optimally protected against COVID-19" by getting vaccinated and getting a booster. If you got one of the mRNA vaccines from Moderna or Pfizer, the CDC says you should get a booster at least five months after your second dose. If you got the Johnson & Johnson vaccine, see the next section.

The Moderna vaccine, Spikevax, has been authorized only for adults 18 and up. The FDA has approved the Pfizer vaccine for people 16 and up, and given emergency authorization for children 5 to 15 years old. 

On Jan. 5, the CDC expanded its recommendation on booster shots to include teens ages 12 to 17. "It is critical that we protect our children and teens from COVID-19 infection and the complications of severe disease," Walensky said. "This booster dose will provide optimized protection against COVID-19 and the Omicron variant. I encourage all parents to keep their children up to date with CDC's COVID-19 vaccine recommendations."

What about the Johnson & Johnson vaccine?

The CDC website indicates "optimal" protection after receiving a second shot of the one-dose J&J/Janssen COVID-19 vaccine at least two months after the first.  

Last year, the agency recommended Moderna or Pfizer's mRNA vaccines over Johnson & Johnson's viral-vector shot, citing a rare but dangerous blood clot side effect. But a booster of Johnson & Johnson's vaccine provides strong protection against the omicron variant of COVID-19 -- stronger even than Pfizer's jab -- according to new research. 

A Dec. 30 study of 69,000 South African health care workers found that, among individuals who already received one dose of the J&J vaccine, a booster given six to nine months later improved their odds against hospitalization from 63% to 85%. 

A separate study by Boston's Beth Israel Deaconess Medical Center found a J&J booster given to individuals who were initially given two doses of Pfizer's mRNA vaccine generated a 41-fold increase in antibody response within a month, compared with only a 17-fold increase when given a booster of the Pfizer vaccine.

For more, here's what we know about the omicron variant and how the new mutation compares with delta. And here's how to store your vaccine card on your phone.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.