CDC Recommends People Stay 'Up to Date' on COVID Vaccines—Here's What That Means

The Centers for Disease Control and Prevention announced on Wednesday that it is not changing the definition of what it means to be "fully vaccinated"—even with the emergence of the highly transmissible Omicron variant and booster dose availability—but that it will be urging people to remain "up to date" on their vaccine schedule.

The announcement came during a White House COVID-19 Response Team press briefing, and was followed by the addition of a webpage on the CDC's website titled "Stay Up to Date with Your Vaccines."

The CDC states that, outside of a primary series of a COVID-19 vaccine, people should "remain up to date with their vaccines, which includes additional doses for individuals who are immunocompromised or booster doses at regular time points." The agency adds that people who are moderately or severely immunocompromised may get an additional dose and a booster dose.

This new term doesn't necessarily clarify the already muddy waters of vaccine status—especially when multiple vaccines are available with varying effectiveness and the ability to mix-and-match those vaccines exists—but it does provide some extra guidance for optimal protection. Here's what you need to know right now, according to experts, about what it means to be "up to date" on your vaccination status, and how it differs from being "fully vaccinated."

What Does It Mean To Be "Fully Vaccinated" Right Now?

When COVID-19 vaccines began going into arms in late 2020, the definition of "fully vaccinated" was clear: It meant a person had received the final of two doses of an mRNA vaccine, or a single dose of the Johnson & Johnson-Janssen (J&J) vaccine. That guidance hasn't changed, nor are White House officials planning on changing it anytime soon.

According to the CDC, everyone in the US over 5 years old is recommended to receive a primary series of a COVID-19 vaccine. For children and teenagers ages 5–17, that means two doses of the Pfizer-BioNtech vaccine. For people ages 18 or older, a primary series can mean two doses of any mRNA vaccine (Pfizer or Moderna), or a single dose of the J&J vaccine. Of all three vaccine options available in the US, the CDC says the two-dose mRNA vaccine are preferred over the J&J vaccine.

What Does It Mean To Be "Up to Date" on Your Vaccines?

Basically, being "up to date" on your vaccines includes any additional shots you can get, past your primary vaccine series, when you're eligible. That means additional doses for those who are immunocompromised and booster doses for everyone else. (Some immunocompromised individuals may even get an additional dose plus a booster dose.)

The eligibility for those booster doses depends on which vaccine you received for your primary series, and when you received it.

According to the CDC, anyone 12 years of age or older who received the Pfizer vaccine as a primary series is eligible to get a booster dose at least five months after their second shot. For kids ages 12–17, that booster dose must be another Pfizer vaccine; for anyone 18 or older, any mRNA vaccine is preferred.

For people who received the Moderna vaccine initially (anyone 18 or older), they're eligible to get a booster dose at least six months after their primary series—again, with an mRNA vaccine preferred in most situations, per the CDC.

Those who opted for the single shot J&J vaccine have slightly different instructions: They're eligible to receive a booster dose at least two months after their initial vaccine, and are also urged to opt for an mRNA vaccine booster. (Note: While the CDC strongly urges that people stick to mRNA doses right now, it does say the J&J vaccine could still be considered in some situations.)

How Does Being "Up to Date" Differ From Being "Fully Vaccinated"?

When the CDC references being "up to date" on your vaccination status, what they really mean is that you have the optimal protection available against COVID-19, Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York, tells Health.

The reasoning here: Protection from vaccines can wane over time, and effectiveness can be threatened by variants of the virus. The CDC specifically points to the increased risk of breakthrough cases with the Omicron variant that's currently dominant in the US. According to CDC data shared in November, people who were unvaccinated were three times more likely to test positive for COVID-19 than those who were vaccinated, and nine times more likely than those who were vaccinated and had received a booster dose.

That said, even a primary series of the vaccine does a very good job at what it's meant to do: prevent severe illness, hospitalization, and death. "When it comes to what matters—serious illness and keeping people out of the hospital—those who have had two doses of an mRNA vaccine or one dose of the Johnson & Johnson vaccine are protected," Amesh A. Adalja, MD, an infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security, tells Health.

That's an important piece of the puzzle, and it's likely why the CDC didn't change its stance on what it means to be "fully vaccinated" overall. "You can't say that someone who has had two doses of the Pfizer or Moderna vaccine is the same as someone who has had nothing," says Dr. Adalja. The standardization of the "fully vaccinated" language is important too, since that status allows people access to certain workplaces, college campuses, restaurants, or public events.

As of right now, 62.4% of the US population is considered "fully vaccinated," according to the CDC. That number drops to just 35.3% regarding those who have received a booster dose and are considered "up to date." For now, the two vaccine statuses remain separate—while still pushing for citizens to receive optimal protection when they can. "They're not saying that in order to be 'fully vaccinated' you need to get a booster," says Dr. Russo, "But they're saying that you really should get a booster when you're eligible."

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.