Nearly one year ago, the first COVID-19 vaccine was administered in the United States. Now, with more than 400 million COVID-19 shots given to American citizens, U.S. health regulators are discussing whether people need to get a booster shot or a third dose to help them maintain their immunity against the virus.
But how do you tell the difference between a booster shot and a third dose? Who qualifies for one or the other?
We brought these questions to Edward Walsh, MD, an infectious disease specialist with Rochester Regional Health, to give us more insight into what the differences are and why they matter.
First of all, confusion about a COVID-19 booster shot being different from a third dose of the COVID-19 vaccine is understandable. For the mRNA vaccines (Pfizer and Moderna vaccines), the initial immunization schedule requires two doses 3-4 weeks apart - at which point you are considered fully vaccinated.
A booster dose for these two vaccines refers to a third dose, which is generally given many months later. However, for the Janssen (Johnson & Johnson) vaccine that only requires one dose in the initial vaccination schedule, a booster would be considered a second dose of this vaccine, also given many months later.
Generally a booster shot is given to someone after their initial immunity to a disease starts to drop off over time. The booster shot does what its name suggests: it gives a boost to the immune system and helps it continue protecting the body against infection.
Following reviews of recent vaccination data, the CDC issued recommendations on September 24 and October 21, 2021, authorizing booster doses of the Pfizer-BioNTech, Moderna, and Johnson & Johnson COVID-19 vaccines to be given to certain groups of people whose immunity to COVID-19 may be dropping off. That lessened immunity can result in increased risk of infection – often referred to as “breakthrough” infections.
At this time, a third dose of the fully FDA licensed Pfizer mRNA vaccine has been recommended by the CDC for certain groups of people, including persons over the age of 65, those under age 65 with certain underlying heath conditions, immunocompromised persons, and those at high risk of contracting COVID-19 (such as health care workers and teachers).
These people can receive a third (booster) dose if it has been at least 6 months since their initial immunization. Immunocompromised persons (see below) can be given a booster dose sooner than 6 months. The third dose can be given to these patients, according to current CDC guidance, at least 28 days after the person’s second dose.
Different groups of people qualify for each kind of shot.
For the booster shot, the following groups of people are recommended by the CDC and FDA:
The CDC and FDA recommend a third dose of the Pfizer or Moderna COVID-19 vaccine be given to people with “moderately to severely compromised immune systems.” Some of these immunocompromised people include:
“Scientists are still reviewing data when it comes to children and COVID-19 vaccines,” Dr. Walsh said. “Since the Pfizer vaccine is the only one currently under emergency use authorization for children ages 12-15, any decision on booster shots or third doses for children in the near future would apply to that vaccine.”
The guidelines regarding the benefit and safety of mixing different vaccines is different for initial immunization, booster shots, and third doses.
On October 21, 2021, the CDC issued new guidance that allows for any COVID-19 vaccine with emergency use authorization to be used as a booster shot for the groups of people outlined above.
When it comes to third doses of the Pfizer or Moderna vaccine, experts say attempts should be made to match the third dose to the original two-dose vaccine. However, if that same type of vaccine is not available, patients can have another mRNA vaccine administered, according to the New York State Department of Health.
For example, if a person received the two-dose Pfizer vaccine and is eligible for a third dose but only additional doses of the Moderna vaccine are available at a location, they can receive the third dose of the Moderna vaccine.
Mixing and matching initial immunization doses (i.e., a first dose of Pfizer and a second dose of Moderna) remains under study at this time.
Qualifying individuals are the only ones who are currently eligible to receive booster shots or third doses of the COVID-19 vaccine.
Rochester Regional Health will be offering booster shots and third doses of the COVID-19 vaccine in the near future. Providers will contact eligible patients once the doses become available.
Starting October 1, Monroe County Public Health will be taking appointments for booster shots at the Monroe County Fleet Center in Chili and the Monroe Community College Downtown Campus in Rochester. Appointments can be made by calling (585) 753-5555.
A list of pharmacies and public health agencies offering booster doses or third shots is also available on the Finger Lakes Vaccine Hub website.
If you have questions about whether you should receive either a COVID-19 booster shot or a third dose of the COVID-19 vaccine, contact your primary care provider.
With information and misinformation abundant online, we took the time to bring some of the most common questions about the vaccine to our expert doctors and researchers.Schedule An Appointment
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