Fully Vaccinated? Could There Still Be a Booster in Your Future?

Fully Vaccinated? Could There Still Be a Booster in Your Future?

By Howard Wolinsky

As of May 20, 48.4% of the U.S. population ages 18 years and older is fully vaccinated against COVID-19, and 60.5% have received at least one dose of a COVID-19 vaccine, according to the federal Centers for Disease Control and Prevention.      

But even the fully vaccinated are not done with taking precautions. Vaccine experts say that the fully vaccinated may require a booster shot, or a follow-up vaccination, in the future.

Vaccine manufacturers already are studying the need for booster shots for COVID-19. But experts are divided.

“It looks like you’re going to need a booster in eight to 12 months after your original shot,” said Robert Murphy, MD, the John Philip Phair Professor of Infectious Diseases at Northwestern University Feinberg School of Medicine, where he serves as executive director of the Institute for Global Health.

Anthony Fauci, MD, director of the U.S. National Institute of Allergy and Infectious Diseases and the chief medical advisor to President Biden, told a Senate subcommittee,  “I don't anticipate that the durability of the vaccine protection is going to be infinite. It's just not. So, I would imagine we will need, at some time, a booster."

Pfizer CEO Albert Bourla told Axios recently that a booster shot will likely be necessary "sooner rather than later." He said that booster shots could be needed as soon as September for the earliest vaccine recipients.

Pablo Penaloza-MacMaster, PhD, assistant professor of microbiology-immunology at Northwestern and a member of the CoVAXCEN coalition, said: “It is not clear if we would need a third booster with the same vaccine, or an updated 2.0 vaccine based on the different genetic sequences present in the variants. We have to wait and see.”

Virologist Judd Hultquist, PhD, assistant professor of medicine in the Division of Infectious Diseases at Feinberg, and associate director of the new Northwestern Center for Pathogen Genomics and Microbial Evolution, noted that boosters are used for a couple of different purposes. Sometimes they are needed to improve immune memory over a long period of time, such as a tetanus booster, while other times they can be used to account for a viral population that is rapidly changing, such as the annual flu shot.

 “Boosters can include changes to the vaccine formula to protect you against new versions of the virus. For example, the flu shot changes every year to account for new versions of the flu virus that are circulating,” he said. “Other times, a booster is needed because your own natural defenses slowly decay over time. Tetanus is a great example. While the pathogen that causes tetanus isn’t changing very much over this time, every ten years you need a booster to make sure you remain protected because the number of cells that are actively patrolling for the bug slowly will drop over time.”

Hultquist said the need for boosters with COVID-19 – both if and when they would be needed and what they would consist of - is the focus of research and is still an unsettled question.

“There is a huge debate right now, and we really don’t know yet.  When you get an mRNA [messenger RNA] vaccine, you get a booster shot within three to four weeks after your first shot. That sequential introduction of antigen will increase the amount of antibody that you can produce and how quickly you can mount a defense. That’s one theory as to why the vaccines are so effective.”     

Murphy, co-founder of Northwestern University's CoVAXCEN, a coalition of academic, government and industry experts on the COVID-19 pandemic, said boosters are already being tested, including shots that combine COVID-19 protection with seasonal influenza vaccinations.  

He noted that the Moderna and Pfizer-BioNTech COVID-19 vaccines received emergency use authorization from the U.S. Food and Drug Administration before the variants of the original COVID-19 virus were recognized. Now, the dominant virus in the United States is the Alpha variant (formerly referred to as the B.1.1.7 lineage of concern), first identified in the United Kingdom in the fall of 2020.

But Murphy said the original vaccines provide protection against the most common variants, but new versions of the vaccines have incorporated more specific protection against these variants. The mutant viruses may or may not be more deadly than the original virus, but they definitely are able to infect cells more easily.  

Penaloza-MacMaster said, “In terms of variants, the vaccines are still effective at preventing severe disease/death caused by the original virus or the variants. However, vaccines are not perfect and some infections may occur in vaccinated individuals; this is what we call “breakthrough infections.” There is of course a difference between infection and disease, and not all people who get infected develop disease.”

The immunologist said if one analyzes “breakthrough infections”--infections that occur in a very small fraction of people who are vaccinated—90-95% of vaccinated people can show protection from infection.

“Now, if you look at the 5-10% of vaccinated individuals who get infected, you can see that there’s a disproportionate percentage of breakthrough infections caused by variants (more than the percentage in non-vaccinated people),” he said. “In other words, the number of overall infections in vaccinated people is significantly lower than that in unvaccinated people. However, if you look at vaccinated people, the percentage of infections that are caused by variants is higher than that of unvaccinated individuals. These data suggest that variants could be responsible for many breakthrough infections.”

Penaloza-MacMaster said SARS-CoV-2 is evolving and creating variants, but the virus is still behaving mostly like SARS-CoV-2 and not another virus strain.

“It is best to be cautious. But the fact that there are variants does not really change how we should continue with our daily precautions, especially if we have not been vaccinated,” he said.  “At the same time, it seems that the vaccines are still effective at preventing severe disease/death, and that the variants are not completely overriding vaccine-elicited immune responses. This is in part due to T cells [part of the immune system], and the fact that they can recognize parts of the virus that don’t change from variant to variant.”

Headquartered in the Institute for Global Health's Center for Global Communicable and Emerging Infectious Diseases with the cooperation of the Center for Communication and Health, we seek to achieve consensus on a variety of issues related to the safety and efficacy of COVID-19 vaccines and then produce and disseminate written materials for scientists, healthcare professionals, and the general public describing its conclusions.

Northwestern COVID-19 Vaccine Communication and Evaluation Network (CoVAXCEN) seeks to achieve consensus on a variety of issues related to the safety and efficacy of COVID-19 vaccines and then produce and disseminate written materials for scientists, healthcare professionals, and the general public describing its conclusions.

Howard Wolinsky is a Chicago-based freelance medical writer and author. He is the former medical reporter for the Chicago Sun-Times. He has won awards for medical writing from the American Public Health Association, the American Bar Association, and the Association of Health Care Journalists, and the Chicago Headline Club. The Sun-Times twice nominated him for the Pulitzer Prize