How Do You Know If You Need a COVID-19 Booster Shot?

May 20, 2022 - Katie McCallum

The COVID booster conversation has gotten confusing.

You may have heard that kids ages five and up are now eligible to receive a booster dose of the Pfizer vaccine.

And what's this about second boosters for some adults?

There's also still the lingering question you may have of whether you and your family really need more doses or not...

Dr. H. Dirk Sostman, chief academic officer of Houston Methodist, is here to answer common questions you may have about getting a booster dose.

Are booster shots actually necessary?

A booster is an additional dose of vaccine that can help prolong protective immunity in someone who responded fully at first, but there's evidence that protection is declining after some time.

"In essence, it's a 'top-up' of a person's antibody-mediated immune response to the first vaccine series," says Dr. Sostman. "Circulating antibodies are the first line of defense against getting infected or becoming ill if you are infected."

For people who received the two-shot series of Pfizer or Moderna or single shot of Johnson & Johnson, a booster dose is any dose that follows your initial vaccine series. For people who are immunocompromised and received three shots as part of their initial COVID-19 vaccine series, a booster dose is your fourth dose.

Boosters are being recommended because data is showing that protection against mild and moderate COVID-19 via the initial vaccine series declines over time — particularly for those who were vaccinated some time ago, and even in kids.

Certain people are even eligible for a second booster, such as those who are over the age of 50 or immunocompromised, since there is concern that boosted protection is already starting to wane in these individuals.

Who is eligible for a booster dose or doses?

The simplest place to start when considering whether you can get a first or second booster is to consider:

  • Your age
  • Whether you are immunocompromised

Anyone who is 18+ may also need to consider which COVID-19 vaccine they initially received.

COVID Booster Eligibility:

Kids Ages 5 to 11

Kids ages 5 to 11 are eligible for a booster dose of the Pfizer vaccine after five months have passed since their initial vaccine series.

Children under the age of 5 are not yet eligible for COVID-19 vaccination.

Teens ages 12 to 17

Teens ages 12 to 17 are eligible for a booster dose of the Pfizer vaccine after five months have passed since their initial vaccine series.

Teens who are immunocompromised are also eligible for a second booster dose four months after the first booster dose.

Everyone 18+

All adults who are 18+ are eligible for a booster dose of the COVID-19 vaccine.

If you're 50+ or you're immunocompromised, you may be eligible for a second booster shot as well.

When you should get your booster shot(s) depends on:

  • Which vaccine series you initially received
  • Your age
  • Whether you are immunocompromised

Use the CDC's COVID booster tool to determine if and when you may need a first or second booster.

People Who Are Immunocompromised (Ages 5 & Up)

For those who are moderately or severely immunocompromised and at least five years of age, booster shots are recommended.

If you are 12+ and immunocompromised, you may also eligible for a second booster dose.

A person is considered immunocompromised if he or she:

  • Is actively being treated for a solid tumor or blood cancer
  • Has received a solid-organ transplant and is taking immunosuppressive medications
  • Has received a stem cell transplant in the last two years
  • Is actively being treated with certain immunosuppressive medications, including high-dose corticosteroids
  • Has a moderate or severe primary immunodeficiency, such as DiGeorge and Wiskott-Aldrich syndromes
  • Has advanced or untreated HIV infection

Use the CDC's COVID booster tool to determine when and which COVID vaccine you should receive as your booster, which can vary based on age and which vaccine you initially received.

If you don't meet these criteria, you may still be able to get a booster shot via a doctor-prescribed dose.

Because both vaccines are fully approved by the FDA, your doctor can choose to prescribe another dose of either of these vaccines as a booster, based on his or her best judgment for off-label prescribing.

In addition, the FDA and CDC have also authorized the use of heterologous (or “mix and match”) booster doses for people who 18 years of age or older, meaning adults can receive a booster of either Pfizer or Moderna.

How do you know if you actually need a booster? Do your antibody levels matter?

"If you're eligible for a booster but aren't convinced you need another dose, consult your doctor. He or she can help you make a decision based on your individual benefits and risks of getting an additional dose," adds Dr. Sostman.

One such way your doctor may choose to help make this decision is to check your antibody levels, also called antibody titers. There are many components to immunity, and antibodies are an important one — especially in the early stages of infection.

"COVID-19 vaccination elicits robust antibody production in most people, but the levels of these antibodies wane over time," explains Dr. Sostman. "If you're unsure whether you need a booster, your antibody titers can be one piece of information your doctor uses while counseling you on your decision. If your titers are very low, a booster shot may be recommended. However, we do not recommend routine use of titer measurements."

Can you mix and match vaccines during your booster?

If you are 18+, you are able to choose which vaccine you receive as a booster dose if you meet the criteria above for a such a dose.

For these adults, the known and potential benefits of receiving a different vaccine as a booster dose outweigh the known and potential risks of mixing and matching.

Do you still need a booster if you've recently had COVID-19?

COVID-19 immunity is complicated, especially for those who have both natural immunity (from recent infection) and vaccine-induced immunity. Understanding how these two might work together and whether protection can be additive has yet to be answered.

"We know that having COVID-19 can elicit an increase in antibodies that protect you from re-infection with the virus, so there's likely some time in which natural immunity can act as a 'booster'," says Dr. Sostman.

He points out that we don't know how long this might last, though, so eventually you will still need an actual booster shot.

"In addition, there is some data suggesting that COVID-19 infection followed by vaccination may provide extremely strong immunity, but we just do not have enough data to know whether this can substitute for a vaccine booster shot," he adds.

If you have recently had COVID-19 and are eligible for a booster, it's recommended that you get your shot after your symptoms have resolved and the recommended time has elapsed since your primary series of vaccine. People who received monoclonal antibodies as part of their COVID-19 treatment plan will need to wait 90 days before getting a COVID booster.

How do you actually get your COVID booster?

If you need a COVID-19 vaccine or booster, you can schedule an appointment with a primary care doctor near you or get vaccinated at a local pharmacy.

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