Jan 11, 2022
Answers to common questions about COVID-19 boosters
The CDC is urging anyone who is eligible to get a COVID-19 booster shot, amid the swift rise of the Omicron variant.
"Current data demonstrate that receiving a booster dose is critical to provide protection against COVID-19 and the Omicron variant," said Centers for Disease Control Director Dr. Rochelle Walensky in a recent briefing. "Vaccines and boosters are protecting people from the severe and tragic outcomes that can occur from COVID-19 infection."
After first being detected in the U.S. on Dec. 1, 2021, Omicron rapidly spread across the country to make up more than 98% of all COVID cases nationwide by Jan. 8, 2022, an indication of its extraordinary transmissibility even in vaccinated people. However, booster shots are proving effective in preventing infection and severe illness, health officials say.
"Omicron evades immune vaccine protection against symptomatic disease and, to some extent, to severe disease," said Dr. Anthony Fauci, President Biden's chief medical advisor. "However, laboratory and clinical data indicate that booster shots reconstitute vaccine protection, even against Omicron."
Anyone 12 or older who who received a Pfizer-BioNTech or Moderna COVID-19 vaccine is eligible for a booster shot five months or more after their last shot, per CDC guidance. Any adult who got the J&J COVID-19 vaccine can get a booster shot if they were vaccinated two or more months ago.
Kids and teens can get a Pfizer booster shot. For adults, the CDC has endorsed a so-called “mix-and-match” approach, saying eligible people fully immunized with one company’s vaccine can receive a different vaccine for their booster shot if they wish.
The concept of booster shots is far from new – they are given for a range of illnesses including chickenpox, tetanus, diphtheria, mumps, measles, and rubella.
Coverage spoke to Dr. Simone Wildes, an infectious disease specialist at South Shore Health and a member of the Massachusetts Department of Public Health’s COVID-19 Health Equity advisory group, about how boosters work and why they will play a crucial role in combating COVID-19.

Why do we need boosters for COVID-19?
All three COVID-19 vaccines authorized in the United States are safe, and they have remained highly effective at preventing death and, in many cases, severe illness.
However, like many other types of vaccines, recent research shows a decrease over time in protection from asymptomatic or mild infection, particularly in people 60 or older. Research shows increased immune response in booster recipients, indicating improved protection.
“The vaccines are still very effective, but there has been some reduction in protection against infection, particularly with the Delta and Omicron variants,” Wildes said. “The booster can strengthen immunity.”
How do boosters work?
An initial COVID-19 vaccine dose prompts your body to activate antibodies and T-cells – two key players in the immune response that mobilize and attack when there is an invader like the novel coronavirus.
“If there has been a decrease in immune response over time, you may not get the same robust response when infected,” Wildes said. “A booster shot will remind those cells to protect the body.”
A booster shot causes antibody-making B-cells to multiply, once again increasing the number of antibodies against COVID-19.
Boosters "lift up the level of the neutralizing antibodies high enough that it generally crosses over and covers several of the variants," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and chief medical advisor to the president, in a Nov. 28 interview about Omicron. "I don't think there's any possibility that this could completely evade any protection by a vaccine. It may diminish it a bit, but that's the reason why you boost."
What is the difference between a third dose and a booster shot?
It is important to note that a third dose and a booster are not the same, Wildes said.
“An additional dose for someone who is immunocompromised, as opposed to a booster for someone healthy, is a different thing,” she said. “For someone who is immunocompromised, they don't develop immunity from the first dose the way a healthy person does, so they get an additional dose.”
The FDA and CDC have approved third doses for immunocompromised patients, including:
- Patients receiving active cancer treatments.
- Organ transplant patients.
- Recent stem cell transplant patients.
- Patients with advanced or untreated HIV infection.
- Patients with moderate or severe immunodeficiency.
- Patients being treated with medication that suppresses the immune system.
Why should I get a booster?
“In trying to stay as healthy as possible and trying to avoid getting and transmitting COVID-19, it's very important to get a booster shot,” Wildes said.
As protection continues to decrease, vaccine recipients will experience more breakthrough infections, Wildes said. And if those infections keep rising, we will continue to see deadly surges among the unvaccinated – potentially giving rise to more dangerous new variants as well.
Wildes noted that although some people – especially those who had side effects after the initial vaccine shots – may not be keen on getting a booster, it is more than worth it.
“It may be inconvenient, but based on what I've seen and how devastating the disease can be, I will be the first in line,” Wildes said. “When you think about having your lungs, your brain affected, and other systems in your body affected long-term by the virus, it's a no-brainer. It’s a small price to pay for staying healthy.”
Boosters, like all COVID-19 vaccines, are free and widely available. You can sign up for an appointment in Massachusetts through VaxFinder or by calling 211.
PHOTO OF DR. SIMONE WILDES BY FAITH NINIVAGGI