What does it mean to be fully vaccinated?

What does it mean to be fully vaccinated against COVID-19? It’s a question that up until recently seemed fairly straightforward.

First it meant one or two shots, depending on which vaccine you got, plus a two-week period to allow for maximum immune response. Then the summer surge, driven by the delta variant, started to raise questions about whether we needed more protection. But since late last year, the emergence of the omicron variant has turned a debate about language and definitions into a matter of public health urgency. The variant’s ability to reinfect people brought into sharp focus the need for booster doses to bolster waning immunity and to prevent severe outcomes, hospitalization and death from the coronavirus.

Dr. Emily Hyle, an infectious disease specialist at Massachusetts General Hospital, said that prior to omicron she had been “much more on the fence” about booster doses going to people who were not at high risk of disease. Now, after observing how the pandemic has shifted even in her own practice, Hyle said she will ask anyone: “Have you gotten your booster?”

As doctors have adjusted their own recommendations, so have businesses and employers. Restaurants in many parts of the country require proof of vaccination to dine, and many employers have mandated shots for people doing on-site work. Depending on where you live or work, being up to date on vaccinations could require a booster. On Jan. 13, the Supreme Court ruled that large employers could not require workers to be vaccinated, but that health care workers were beholden to vaccine mandates. But if that proof of vaccination itself is coming into question, how should businesses and schools adapt?

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Using the term fully vaccinated “becomes a public health miscommunication,” said Dr. Ali Ellebedy, an immunologist at the Washington University School of Medicine in St. Louis, as we look to the future when we may face more variants. “If we call [patients] fully vaccinated and we get pi or tau or a virus strain after that, it could be completely different.”

For nearly two years, Americans have been getting a crash course on the evolution of science, data and research – one in which our knowledge and understanding need constant fine-tuning. Doctors and researchers are rethinking how to communicate what it means to have and keep adequate protection against COVID-19 — which affect a person’s individual vaccination status but also what businesses, their employers and transportation providers might ask of them. For people across the country, the subject matter can be incredibly confusing and frustrating, and the stakes of keeping up could not be higher.

The virus has outpaced people’s willingness to get vaccinated and boosted, hampered by political division and misinformation. So far, three-quarters of the total U.S. population – roughly 250 million people – have received their first shot, according to the latest CDC data.

These vaccination numbers are particularly harrowing as the nation approaches a grim pandemic milestone – the death of 1 million people from COVID-19. Just a little more than a quarter of everyone in the U.S. – 88 million people – have gotten boosted – about four out of 10 people who already had received their primary series.

In addition to the health risks of not being “fully vaccinated,” there are other real-world consequences.

Unclear guidelines around vaccination status could worsen long standing issues of inequity and access to travel, services and jobs, said Dr. Walid Gellad, professor of medicine at the University of Pittsburgh.

“What does it really mean economically?” he said. “What would that mean if you change it to three doses?”

Why experts are rethinking the definition

Weeks after learning about the existence of SARS-Cov2, scientists had sequenced the virus, begun work to develop the vaccines and launched the first phase of clinical trials. These two-dose vaccines were authorized in December 2020.

In recent weeks, given the more transmissible variants, the Centers for Disease Control and Prevention hasn’t officially changed their definition of “fully vaccinated,” but it has urged the public to stay “up-to-date” on their COVID vaccines. What does that mean?

  • If five months have passed since your last Pfizer or Moderna dose — or two months since your single Johnson & Johnson dose — then it’s time to get boosted.
  • If you aren’t vaccinated, get your primary series right now.

If you ask Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor University, the FDA-approved mRNA vaccines should have always been three doses – not two. A pediatrician by training, Hotez said children’s vaccines often include an initial series followed by a booster shot to enhance protection.

“Now, that’s clearly borne out by the omicron data where you need a third dose to get adequate protection from hospitalization,” Hotez said.

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During an interview with PBS NewsHour chief correspondent and substitute anchor Amna Nawaz, Moderna chief medical officer Dr. Paul Burton agreed that people shouldn’t consider themselves fully vaccinated unless they had had three shots. Boosters are “what will provide maximal protection,” he said.

Why language matters

To convince the public to get vaccinated, President Joe Biden and top scientists like Dr. Anthony Fauci of the National Institutes of Health have repeatedly asked the public to get “fully vaccinated” – saying that would stop the virus in its tracks and prevent it from spreading further. Those messages were clear at the time, but offered little room to adjust when the situation changed, as it did with delta and omicron.

Authorities delivered those statements with certainty because that data-backed guidance was a reflection of the world where we lived, Gellad said. But vaccine resistance was greater than experts calculated, and public adoption far slower – allowing the virus to further evolve.

“There was too much certainty placed on two shots,” Gellad said.

Less than a year after those vaccines became available, debate among public health officials began over whether people needed a booster dose to improve their immunity. Part of that debate was rooted in concerns about global vaccine equity. Worldwide, data suggest more than half the global population is vaccinated, but in low-income countries, about one out of 10 people are estimated to have received their first dose.

READ MORE: COVID helped cause the biggest drop in U.S. life expectancy since WWII

Hotez said that messaging that adopted a similar approach to the way we approach kids’ routine vaccines should have been used in getting the public ready for COVID-19 boosters as soon as vaccines were rolled out.

After months of conflicting messages from then-President Donald Trump’s administration and top scientists, federal agencies under the Biden administration are now “trying to speak with one voice to the country,” Hotez said. But the message is coming across as “baby talk,” especially amid protracted political divisions, he said.

“We’re doing terribly in terms of boosters, and we’re paying the price for that,” he said.

But all is not lost. Hotez said federal officials can still – and must – explain to the public why they need boosters, since another variant will likely inherit omicron’s chaos until there is more robust vaccine coverage in the U.S. and around the globe.

“There needs to be a vaccine strategy of how to manage the next wave,” he said.