What’s the difference between a 3rd vaccine shot and a booster shot?

·4 min read

The Centers for Disease and Control and Prevention endorsed booster shots of Pfizer's COVID-19 vaccine for vulnerable and older Americans on Thursday, which are not to be confused with third doses of the vaccine.

Walgreen's chief medical officer, Dr. Kevin Ban, helped outline the difference between a booster shot and a third shot of the vaccine on the 3rd hour of TODAY Friday as Walgreen's prepares to offer booster shots of the Pfizer-BioNTech vaccine to those who are eligible.

"I want to differentiate here between a third dose and a booster dose," Ban said. "If you’re immunocompromised, if your immune system doesn’t do the job that it usually should, usually because you have a medical condition or are on certain medications, what we saw is that after two doses for Pfizer and Moderna, after one dose for J&J (Johnson & Johnson), there just wasn’t an adequate enough immune response, and so those people need a third dose.

"They need a third dose to get the immunity to the level where it will protect, which is very different than a booster dose."

Those receiving a third dose of the vaccine have conditions like cancer, an organ or stem cell transplant, HIV or are being treated with high-dose steroids that could suppress the immune system.

"The third shot refers to completing the original vaccine series if you're immunocompromised, so you need three shots to be fully vaccinated," NBC News contributor Dr. Kavita Patel, a primary care physician in Washington, D.C., told TODAY.

A booster shot, on the other hand, is an additional dose needed after the protection of the initial dose or doses has lessened over time, according to experts.

"Think of the boost as recommended," Patel said. "I think it's a very good idea, but it does not change the fact that you had full immunization. You're still fully vaccinated without the booster."

"A booster dose, a person got the immunity after the first run of the vaccine, and now over the course of time — and it’s looking that's somewhere around six months — we start to see waning immunity," Ban said. "Then those people need to have their immune system boosted, and so that’s a very different thing."

On Thursday, CDC Director Dr. Rochelle Walensky endorsed recommendations from a panel of advisers that said people 65 and older, nursing home residents and people ages 50 to 64 with underlying health problems should be eligible for a booster shot at least six months after their last Pfizer shot.

Walensky also added those ages 18 to 49 with underlying health conditions and those 18 to 64 who work in high-risk environments like health care workers and teachers to the list of those eligible for a Pfizer booster shot.

The booster shots currently are only for those in eligible groups who previously received the Pfizer shots. Booster shots for the Moderna and Johnson & Johnson vaccines have not been approved yet, and there is little data about the effects of mixing and matching those vaccines with a Pfizer booster shot.

Patel said she is encouraging people not to mix and match the vaccines if they have previously had Moderna or J&J shots. However, she has recommended a Pfizer booster shot for a high-risk patient in a nursing home who originally had the Moderna shot, so there could be exceptions if someone really needs a boost in immunity.

"If you got the J&J or Moderna (shots) and you're over 65 with certain high-risk conditions, absolutely have a conversation with your physician (about getting a Pfizer booster shot)," Patel said.

All three shots remain protective of serious illness, hospitalization and death from COVID-19, so Ban stressed for those in groups eligible for booster shots not to worry as they wait for Moderna and J& J booster shots to receive approval.

"It’s very important for everyone to know that they are covered with the first doses of vaccine, so they are OK," he said. "Go ahead and get boosted if you got Pfizer and are approved. For people who got Moderna and J&J, you’re still fine, you’re still covered. We expect that those manufacturers will go through the EUA process as well, and then those people can be boosted."

Health experts stress that the most important task in bringing an end to the pandemic is not booster shots, but getting more Americans initially vaccinated. Only about 55% of the population is fully vaccinated.

“We can’t boost our way out of this,” Patel said. “If all 50 million people who got Pfizer shots six months ago go get a booster shot tomorrow, that’s not going to end this. That’s not what’s creating the crisis.”

Walgreen's already has doses of Pfizer booster shots at its stores and is ready to start dispensing them immediately, Ban said. People will need to verify online that they are eligible for the Pfizer booster shot when they make an appointment and then will be vetted again in person.

Ban recommended that those eligible for a booster shot also schedule a flu shot at the same time. He also urged those who aren't yet eligible for a booster shot to still get a flu shot.

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