Millions of Americans now can get COVID-19 booster shots. Everything you need to know.

Sept. 24, 2021
Calvin Burnett shares an elbow bump with Dr. Sunita Sharma, a pulmonary critical care specialist, who volunteered to give vaccines at Colorado's oldest Black church.
Calvin Burnett bumped elbows with Dr. Sunita Sharma after she gave him his first dose of the COVID-19 vaccine at Shorter Community AME Church in Denver. Now health experts at the FDA and CDC are recommending booster shots for older adults and many others. Photo by Cyrus McCrimmon for UCHealth.

By Katie Kerwin McCrimmon and Erin Emery

Millions of people across the U.S. now may get COVID-19 booster vaccine doses after leaders of the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) authorized additional doses of the Pfizer-BioNTech vaccine for a vast swath of U.S. adults.

Who should get booster shots?

The new guidance recommends COVID-19 booster shots for all adults ages 65 and older and authorizes boosters for many others ages 18 and older including health care workers, teachers and people who live or work in high-risk settings like homeless shelters or prisons. Individuals who are at high risk for severe illness if they get COVID-19 — people who are obese, pregnant or suffer from diabetes — also may choose to get booster vaccine doses.

The new recommendations for COVID-19 booster shots come as the highly contagious delta variant has sparked a dangerous new wave of infections and deaths across the U.S. Cases of COVID-19 are rampant now among unvaccinated people, giving the pandemic an extended opportunity to spread around the world.

In Colorado, COVID-19 hospitalizations in September have rivaled peak hospitalizations in the earliest days of the pandemic in the spring of 2020.

And, the overall toll from COVID-19 has been devastating:

  • In recent days, deaths in the U.S. have surpassed 681,000, spiking higher than the estimated 675,000 Americans who died during the 1918-1919 flu pandemic.
  • More than 7,600 people have died so far from COVID-19 in Colorado.
  • About 100 people every hour are dying from COVID-19 now, according to Dr. Matthew Daley, a pediatrician and researcher for Kaiser Permanente in Colorado and chair of the CDC’s working group on COVID-19 vaccines for the Advisory Committee on Immunization Practices (ACIP).
  • Fatalities now from COVID-19 are almost entirely preventable since highly effective vaccines are easy to get and free throughout the U.S.

While COVID-19 infections in unvaccinated people are common this fall, research shows the effectiveness of vaccines wanes over time and booster doses six months or longer after initial doses can jumpstart vaccine efficacy, bringing it back up to remarkably-protective levels of about 95%.

Health experts agree that the best way to end the pandemic as soon as possible is for all eligible unvaccinated people to get their first doses of vaccines as soon as possible. (Learn more about getting COVID-19 vaccines and booster doses.)

But, booster doses for vaccinated people will help prevent breakthrough cases of COVID-19 in immunocompromised people, older adults and other vulnerable people.

“We know booster shots play an important role in the fight against COVID-19, and we’re still in the midst of a pandemic,” said Dr. Michelle Barron, senior medical director of infection prevention at UCHealth. “Vaccine efficacy may diminish over time with the potential risk for increased susceptibility to breakthrough infections.”

Now that booster shots have been formally authorized for millions of other Americans, we’re providing answers to your key questions on COVID-19 booster shots.

What is a booster shot?

A booster shot is an additional dose of a vaccine after a person has received an earlier dose (or two in the case of COVID-19 mRNA vaccines). An extra dose “boosts” your immune system, sparking better protection against an illness.

Why do we need boosters?

It’s normal for some vaccines to wane or become slightly less effective over time. Research both by the COVID-19 vaccine makers and independent scientists is showing that the mRNA COVID-19 vaccines are waning several months after recipients get their first doses. Also, the delta variant is extremely contagious and it has caused hundreds of thousands of new infections. Because of new infections and waning effectiveness of some COVID-19 vaccines, FDA and CDC experts are recommending booster doses for many people.

What is the specific CDC advice about who should get a booster shot?

Joan Hooker, 89, received her vaccine on Sunday at her church, Shorter Community AME in Denver. Who should get booster shots now?
Older adults are among the first who should receive booster shots. Joan Hooker, 90, received her first COVID-19 vaccine doses at her church, Shorter Community AME in Denver. Photo by Cyrus McCrimmon for UCHealth.

The new recommendations from the CDC apply to those who received the Pfizer vaccine and say that:

  • People ages 65 years and older and residents in long-term care settings should receive a booster shot,
  • People ages 50 to 64 with underlying medical conditions should receive a booster shot.
  • People ages 18 to 49 with underlying medical conditions may choose to receive a booster shot based on their individual decisions about benefits and risks, and
  • People ages 18 to 64 who are at increased risk for COVID-19 exposure and transmission because of occupational or institutional setting may choose to receive a booster shot based on their individual decisions about benefits and risks.

When should I get a booster?

The recommended timing is at least six months after you received your first vaccine doses.

What’s the difference between a booster dose and a third shot for immunocompromised people?

A third shot is now the standard initial dose for immunocompromised people. These are people who have specific conditions that make it hard for them to build up antibodies to fight infections.

Immunocompromised people should get a third shot about one month after their first two doses of mRNA vaccines like Pfizer and Moderna.

Booster shots, on the other hand, are for everyone else. Healthy vaccinated people should wait six months or longer after their initial doses to get a booster vaccine dose.

Do I have to have a doctor’s order to get a booster shot?

No. To streamline booster doses, people can “self-attest” that they qualify for a booster dose. Also, no one needs a doctor’s order to get initial doses of COVID-19 vaccines. They are free and easy to find through hospitals, doctor’s offices, pharmacies and at some mass vaccination clinics. Learn more about vaccine locations in Colorado.

How can I get a booster vaccine?

UCHealth patients can log in the online health portal, My Health Connection and can schedule booster doses online. Learn more about COVID-19 vaccines.

How much do booster doses cost?

Booster doses are free, just like the initial COVID-19 vaccine doses.

Can I get a flu shot at the same time I get my booster shot?

woman feeling sick and drinking tea - flu cases could be bad in 2021 and 2022
Medical experts are advising people to get flu shots early since both flu and COVID-19 could be spreading at the same time this fall and winter. Photo: Getty Images.

It’s safe to get flu and COVID-19 vaccines or booster shots at the same time. But, some vaccine clinics only offer COVID-19 vaccines. You may need to schedule a flu shot separately. Please check with your doctor.

Health experts are encouraging people to get both COVID-19 vaccines and flu shots as soon as possible this fall since we may have an early flu season and the U.S. might face a “twindemic” of infectious diseases this fall and winter.

Is it true that the Moderna vaccine is staying effective longer than the Pfizer vaccine?

Yes. Research like this new study in the New England Journal of Medicine is showing that both the Pfizer and Moderna vaccines are highly effective and very safe. It’s also common for some vaccines to diminish in their effectiveness over time. The Pfizer vaccine seems to be waning (or becoming somewhat less effective) more quickly than the Moderna vaccine.

According to new data from the CDC, vaccine effectiveness in preventing hospitalizations for COVID-19 was highest for people who received Moderna vaccines — 93% — compared with efficacy rates of 88% for people who had received Pfizer vaccines and 71% for those who had received the Johnson & Johnson vaccine.

What should people who received the single-dose Johnson & Johnson vaccine do?

Because fewer people received the Johnson & Johnson (J & J) vaccine, there is less research on booster doses for J & J recipients. It’s likely that people who received the J & J vaccine will need boosters. But there are no clear answers yet. Medical experts at the FDA are slated to review booster shots for people who received the J & J vaccine in mid-October.

Are there enough vaccines available in the U.S. for people to get both their initial doses of vaccines and their booster doses?

Yes. CDC health experts say that vaccines are plentiful. So, supply is not a problem. Get your initial vaccines as soon as possible and feel free to get a booster dose if you are eligible.

Who is considered immunocompromised?

  • Cancer patients.
  • Organ and stem cell transplant patients.
  • People with immunodeficiencies.
  • People living with HIV.
  • Patients who are being treated with immunosuppressive medications such as chemotherapy, TNF blockers to stop inflammation tied to rheumatoid arthritis, certain biologic agents like rituximab and high-dose corticosteroids.

Are boosters recommended because of breakthrough cases, COVID-19 infections in fully-vaccinated people?

  • Increases in the number of breakthrough cases of COVID-19 have caused health experts to recommend booster shots for some people.
  • But, most people getting sick with COVID-19 now are unvaccinated. And, an overwhelming majority of hospitalized COVID-19 patients have not been vaccinated.
  • Some immunocompromised people have been getting COVID-19 even if they are fully vaccinated. That’s because their bodies are unable to create the same number of antibodies as healthy people, and thus, they cannot mount the same defense against COVID-19.
  • In particular, people with cancer, rheumatoid arthritis, lupus and patients who have had organ or bone marrow transplants and those who are taking immunosuppressive medications have not been able to build up the same level of antibodies to COVID-19 as people without underlying health conditions.

How long are coronavirus vaccines effective?

Both the Moderna and the Pfizer vaccines — which account for more than 95% of U.S. vaccinations so far — remain highly effective for at least six months after people receive their second dose. The efficacy data is based on studies of how clinical trial participants have fared over time. The efficacy has declined slightly over the summer, both because of the delta variant and the waning effect.

Should I stick with the same vaccine brand that I initially received when I get my booster shot?

Yes, if you received Pfizer, stick with Pfizer for your third shot. The same goes for Moderna. But, if you are unable to get the same type that you received, health experts say it’s OK to get a different mRNA vaccine for your booster dose.

What are the side effects of the third dose?

Only about two million people in the U.S. have received booster doses so far, so it’s unclear exactly what the side effects will be. But, early research is showing that the side effects are similar to those that people experienced when they got their first two doses.

Individuals may experience a sore arm, headache, muscle aches, a low-grade fever or feel tired. These side effects typically last fewer than three days. Experts from Pfizer told FDA and CDC officials during recent testimony that many people receiving booster doses have experienced fewer side effects after third doses than they did with their second dose.

Who should skip booster doses?

Young, fully-vaccinated, healthy people probably don’t need booster doses because the vaccines are working very well to protect them from severe infections, hospitalizations and death from COVID-19, according to CDC experts.

Because the vaccines are holding up so well for young, healthy people, some infectious disease experts were hesitant to recommend booster doses for all adults.

In addition, in very rare cases, young men who have been vaccinated have experienced heart issues known as myocarditis. Due to this very rare vaccine side effect, some younger men, ages 18 to 30, may decide to skip booster doses.

Are people in other countries getting booster doses?

Yes. Israel has led the way. In Israel, older adults began getting booster doses in the early summer and now, anyone who is 12 or older can get a booster dose. Other countries like the United Kingdom and Germany also are offering booster doses.

Is there a test to determine how strong your immunity is against COVID-19?

Yes, there are antibody tests. But, doctors do not recommend antibody testing outside of clinical trials. The best way to stay healthy is to get your primary COVID-19 vaccines as soon as possible, then to get a booster dose if you qualify or fall into one of the recommended groups.

If I had COVID-19 already, do I still need vaccines?

Yes. Studies like this one are finding that vaccines are even more protective than natural antibodies. And, people can get COVID-19 after having previously had it. So, it’s best to get fully vaccinated.

Are antibodies from vaccines or previous infections the only mechanisms in our body that are fighting COVID-19 infections?

No. Researchers are finding that antibodies from vaccines team up with natural “memory” cells in our bodies. These are known as “B” and “T” cells.  CDC researchers estimate that antibodies play a majority role in fighting COVID-19 infections, but “B” and “T” cells are also crucial.

About the author

Katie Kerwin McCrimmon is a proud Colorado native. She attended Colorado College, thanks to a merit scholarship from the Boettcher Foundation, and worked as a park ranger in Rocky Mountain National Park during summer breaks from college. She is also a storyteller. She loves getting to know UCHealth patients and providers and sharing their inspiring stories.

Katie spent years working as a journalist at the Rocky Mountain News and was a finalist with a team of reporters for the Pulitzer Prize for their coverage of a deadly wildfire in Glenwood Springs in 1994. Katie was the first reporter in the U.S. to track down and interview survivors of the tragic blaze, which left 14 firefighters dead.

She covered an array of beats over the years, including the environment, politics, education and criminal justice. She also loved covering stories in Congress and at the U.S. Supreme Court during a stint as the Rocky’s reporter in Washington, D.C.

Katie then worked as a reporter for an online health news site before joining the UCHealth team in 2017.

Katie and her husband Cyrus, a Pulitzer Prize-winning photographer, have three children. The family loves traveling together anywhere from Glacier National Park to Cuba.