Third doses versus booster doses: What’s the difference?

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CRAWFORD COUNTY, Kan. – It’s been less than a week since news about third and booster doses has come out, and local health providers are already seeing interest.

“We started getting quite a few phone calls from people asking if they would qualify, and when we were gonna have that available,” says Crawford County Health Department Director Teddi Van Kam.

“We have seen an interest in both the third dose and the booster,” says Sarah Boyd at Mercy Hospital.

But when and who’s eligible aren’t the only questions they’ve received.

“There’s been a little bit of confusion about third doses versus booster doses,” says Van Kam.

So here’s a breakdown.

Third doses, of either Moderna or Pfizer, are exclusively for people who are immunocompromised. These additional doses were approved by the FDA last week, and are aimed at getting the immune response of someone with a compromised immune system to the same level of immune response as everyone else who’s currently considered fully vaccinated. These people are eligible for an additional dose 28 days after receiving their second dose. The CDC has a more in-depth list of who’s eligible for a third shot here: COVID-19 Vaccines for Moderately to Severely Immunocompromised People

Booster doses are for everyone else. While the CDC does not currently recommend American’s receive a booster dose, HHS has laid out a plan to start offering booster doses of Pfizer’s and Moderna’s vaccines this fall — the week of September 20th. In that plan, HHS says booster doses should be administered eight months after the second dose. So while the vaccine itself is the same, the who, when, why, and what they are called are different.

More information on booster doses can be found here: COVID-19 Vaccine Booster Shot.

“When the information first started coming out it was a little bit vague. So we too sort of wondered as well,” says Van Kam. “But it is… we really want to make sure we’re getting the people who are having more issues, or are immune-compromised, that we’re seeing to their needs.”

Van Kam has also been asked why people should wait eight months to get a booster shot.

“In the information I’ve read, some studies have indicated that some people… their immunity starts to wane somewhat after eight months,” says Van Kam.

Dr. Anthony Fauci has also said that waiting the full eight months would give your body a chance to get used to the vaccine before getting a booster.

Waiting to get a booster would also allow vaccine administrators more opportunity to prepare for when they’ll be doing four different vaccine rounds: first doses, second doses, third doses for immunocompromised, and booster doses.

“Logistics are always going to be a concern. So, we are just trying to work through that process. We have the benefit of having electronic health records to be able to help us track those doses,” says Boyd. “So we do have tools available to help us walk through this process.”

“We’re assuming we will need to expand vaccine clinics — start offering them on Fridays and Mondays, as well as Tuesdays like we are now,” says Van Kam. “As we did for the first go around, we’ll just adjust as we need to so we can meet everyone’s needs.”

The Crawford County Health Department has scheduled their first third dose clinic. It will happen this Friday, at the health department, from 9:00 12:30 p.m., and from 2:00 p.m. to 4:00 p.m. If you plan to attend the clinic, Van Kam says you will be required to sign a form listing your compromised health condition(s) upon arrival. Both Moderna and Pfizer will be available.

Mercy Hospital is currently scheduling appointments for third-dose clinics. You can sign up for an appointment at If you have any questions regarding eligibility, Boyd recommends calling the hospital or reaching out to your normal health provider.

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