"The first group is one that's been eligible for a few weeks now, and those are people with serious immunocompromising conditions that may have kept them from fully responding to the vaccine in the first place," says Dr. Labus. "For example, somebody whose immune system is kind of wiped out by taking immunosuppressive therapy after an organ transplant, they just can't mount as strong of an immune response." The second group is those aged 65 and older and the third is anyone age 18 and older who lives or works in a high-risk environment like homeless shelters or long-term care facilities.
- Brian Labus, PhD, MPH, infectious disease epidemiologist and public health professor at the University of Nevada, Las Vegas
- Jennifer Horney, PhD, epidemiology professor and founding director of the epidemiology program at the University of Delaware
Eligibility for a booster shot only applies to those who received the Pfizer-BioNTech COVID-19 vaccine. Dr. Labus says this is because Pfizer began its research before Moderna or Johnson & Johnson, so it's a few weeks ahead in the approval process.
"As time goes on, you lose some of the immunity you initially got from that vaccine," says Dr. Labus. "If you get a natural coronavirus infection, immunity can wear off pretty quickly. It's just because of the type of response your body gets. It's not the same type of response, not as strong as you would get from say, measles, where you have that lifelong immunity."
Though booster shots have begun to roll out, they remain controversial within the medical community. World Health Organization Director-General Tedros Adhanom Ghebreyesus called for a (largely ignored) moratorium on booster shots until the end of 2021 to prevent wealthier nations from using the shots on already-vaccinated people while people in poorer countries remain unvaccinated.
"We don't have enough capacity to vaccinate every single person on the planet right now," says Dr. Labus. "The mRNA vaccines, those have been products that have been created in the United States, and so we focused on the United States first. Along with that, though, we have the advantage that we get it before anybody else does. And at first, it wasn't an issue because nobody had access, but then it becomes a question of do you give Americans a booster dose while large chunks of the world have no access to vaccine?"
While the use of booster shots on healthy people in wealthy nations leaves the unvaccinated in other countries vulnerable, it also allows for further mutation of the virus to occur, explains Jennifer Horney, PhD, MPH, founding director of the epidemiology program at the University of Delaware. The Delta variant, a more contagious and deadly version of the virus that causes COVID-19, was first identified in India. Only 33 percent of India's population is fully vaccinated while 55 percent of the U.S. population is fully vaccinated.
"Variants occur when the virus is transmitted from person to person. The virus mutates slightly, that's normal, we expect that," says Dr. Horney. "The more it transmits from person to person, the more opportunity it has to mutate, so we need to use the vaccines to stop that transmission."
In the U.S., more people will likely become eligible for the booster shot once researchers know more about the side effects. "The reason we didn't approve the booster for everybody is because the [U.S. Food and Drug Administration] said they want more information," says Dr. Labus. "When you're giving a vaccine, there are always going to be side effects. And we have to balance the risk of those side effects against the risk of the disease, the benefits of the vaccine." One concern is myocarditis, an inflammation of the heart that has been observed in younger people who get the vaccine (it has also been observed in people who catch the virus). "Because that problem happened in younger people, it wasn't a concern to approve a booster dose for older people because they don't have that same risk of that side effects."
Although vaccine efficacy does wane over time, Dr. Labus says those who aren't yet eligible for booster shots shouldn't be worried.
"Even without the booster shot, the vaccine is excellent at preventing hospitalization and death," says Dr. Labus. "And it's still really good at preventing disease to begin with. So people who don't have the booster dose or are not eligible for the booster dose still have good protection against the virus. It's not perfect, but it's still good protection against the virus."
Watch this video to learn about how vaccines work:
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