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What's 'fully vaccinated'? Why experts say the CDC should change how we report data

People lined up to get a COVID-19 vaccine at Miami Dade College North Campus on March 6, 2021
Verónica Zaragovia
People lined up to get a COVID-19 vaccine at Miami Dade College North Campus on March 6, 2021

In this interview, USF epidemiology professor Jason Salemi discusses where things stand with vaccines and how immunity is categorized at this stage of the pandemic.

The COVID-19 vaccines effectively prevent someone from developing severe illness, but the vaccines do lose effectiveness over time.

Jason Salemi, a professor of epidemiology at the University of South Florida College of Public Health in Tampa, recently co-authored a paper with Elizabeth B. Pathak, director of the COVKID Project, on why the federal Centers for Disease Control and Prevention should make new categories of vaccination statuses and present its data consistent with the recommendations to the public regarding optimal immunization against the disease.

WLRN health care reporter Verónica Zaragovia spoke with Salemi about where things stand with vaccines and how we categorize immunity at this stage of the pandemic.
Here is an excerpt of their conversation which has been edited for length and clarity.

Leon County Judge John Cooper on June 30, 2022, in a screen grab from The Florida Channel.
The Florida Channel
Leon County Judge John Cooper on June 30, 2022, in a screen grab from The Florida Channel.

What is the problem with the way the CDC is accounting for fully vaccinated people now?

Right now, a 70-year-old person who received two doses of Pfizer back in January with no booster and another 70-year-old who also got a booster shot three weeks ago, they’d both be classified as fully vaccinated, even though the protection each person has may be very different.

So the term "fully vaccinated" to me implies a person is both fully protected and they're done with vaccination, but I think a classification system that better differentiates between those who have optimal immunization and those with some waning immunity is absolutely warranted. People who are either recently vaccinated with their initial series or people vaccinated a while ago, but who got that all important booster dose. That's what we call optimally immunized.

After looking at the vaccine data that states report to the CDC, tell us about the classification system that you and your colleague suggest would better reflect a person's vaccine-acquired immunization status at this point in the pandemic.

The current classification system almost gave this false sense of security. This notion of, "Oh, we have such a high percentage of the population that is fully vaccinated." Somebody who was maybe vaccinated back at the beginning of this year with no additional doses may not be as protected as they think they are, and so we felt it was important to do a comprehensive analysis, utilize the publicly available information and package it differently to better inform the public on how we are proceeding in terms of immunization and to highlight the importance of coming in and getting that booster dose.

As of the end of November, when we consider all ages together in the United States, about 60 percent of the U.S. population would be classified as fully vaccinated. But half of those people, or about 100 million of them have what the science would say is waning immunity. That is, only 30 percent of the U.S. population is optimally immunized through vaccination.

And so this recognition that we have a long way to go to equip people with a higher degree of protection — that, to me, is very important.

How should we be tallying vaccination status and would that change our response to COVID-19?

We need to make certain the ways in which we present and communicate our COVID-19 data, including the way we classify vaccination status, are consistent with the recommendations to the public regarding optimizing their immunity. So we recommend that the CDC update its COVID-19 data tracker, that they report the number and percentage of individuals who are not immunized, partially immunized, who are immunized with waning immunity and who are optimally immunized.

To really assess what's happening as the omicron variant spreads, we need our important COVID-19 metrics — the cases, positivity, hospitalizations and deaths. We need those provided for each of these vaccination groups, as well as for those with prior infection. Then, will we have solid data for omicron’s transmissibility, its virulence and its immune escape capability. These are data that we can then use to make evidence-based recommendations for people.

That immunity wanes over time — this is nothing new. We recommend an annual flu shot, in part because the influenza virus changes from year to year, but in part because our immune response may not be optimal. And so we recommend that people get the flu shot every year. It seems like, at least right now, that's going to be the same thing. We're going to continue to see variants emerge. Our immune response may wane over time. And so this notion of getting these booster shots is probably going to be something that we're recommending for some time to come.
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Verónica Zaragovia