On Aug. 12, the FDA authorized a third vaccine dose for people who are moderately to severely immunocompromised. Those extra doses of the Pfizer and Moderna vaccines are available at Tarrant County Public Health clinics. The third dose, or booster, is not currently approved for or available to the general public.

What’s the difference between a third dose and a booster? 

Medically, nothing, according to Kenton Murthy, a physician and the assistant medical director at Tarrant County Public Health. There’s also no difference between these shots and the first two people received from Pfizer and Moderna. “Same concentration, same amount,” he said.

Rhetorically, though, they’re used in different contexts. The third dose, or additional

dose, is for people who are so immunocompromised that they didn’t receive adequate protection from the initial shots. The booster, however, refers to another dose of the vaccine for a person whose body built up enough protection after the initial shots, but whose protection wanes over time. 

An Israel study, which has yet to be peer-reviewed, suggests immunity from vaccines may wane after six months. However, “the vaccine seems to be highly effective even after six months compared to the unvaccinated population,” according to the study.

Who can get the third dose now?

People who are moderately to severely immunocompromised. The CDC’s list includes people on chemotherapy, people who’ve received an organ transplant, people with advanced or untreated HIV, and people taking drugs that suppress the immune system. If someone doesn’t know whether or not they’re eligible, Murthy recommends they speak with their health care provider. 

People with these conditions and who’ve received two doses of the Pfizer or Moderna can get the third dose 28 days after their second dose. People who’ve taken the Pfizer vaccine must be 12 years or older to get the third dose; for people who’ve taken Moderna, it’s 18 and up. 

They will get the same type of vaccine for their third dose that they received for their first two — Pfizer and Pfizer, or Moderna and Moderna. “We are currently not mixing and matching,” Murthy said. 

There is currently no additional dose available to people who received the Johnson & Johnson vaccine. 

The U.S. Department of Health and Human Services announced it was prepared to make the booster available to the general public by Sept. 20 if the FDA approves it and the CDC’s immunization advisory committee recommends it. If that’s the case, people will be eligible for the booster eight months after they received their second dose.

How can people who are immunocompromised access the third dose in Tarrant County?

Eligible people can receive the third dose for free at a Tarrant County Public Health clinic without an appointment. They should bring their vaccination card. If they’ve lost their card, they can have it replaced at one of these six clinics for free, according to Brian Murnahan, spokesperson for the health department. 

Initial data suggests they will feel similarly after the third dose as they did after the initial doses, according to the CDC. Meenakshi Ramanathan, an infectious diseases clinical pharmacist in Tarrant County, said she recommends people take a sick day if they can, just in case. 

Will booster shots become a regular thing?

Probably, according to Ramanathan, who also teaches at The University of North Texas Health Science Center.

“I think COVID-19 is the new influenza, and we will periodically need a booster shot or a shot against COVID-19 to protect ourselves and our loved ones,” she said. “Now, how often? I’m not sure what the golden number is.” 

In Israel, for example, people 12 years and older can get a booster five months after they’ve received their second dose. 

If and when a booster becomes available to everyone, who should get it?

Everyone, Ramanathan said. But she realizes some people will be hesitant. 

“It’s important to understand why they’re hesitant,” she said. “If they think they’re fully covered by the two doses already, I think it’s important to tell them that the efficacy of the vaccine wanes over time, especially after six months. And so to improve its efficacy against COVID-19, which appears to be a moving target with the variants, another dose is needed.”

Murthy’s central recommendation is still for everyone to be vaccinated, period. “While masking, social distancing and hand hygiene are great tools, this vaccine is our most powerful tool,” he said. “Because I know all of us are fatigued from COVID-19.”

Alexis Allison is the health reporter at the Fort Worth Report. Her position is supported by a grant from Texas Health Resources. Contact her by email or via Twitter. At the Fort Worth Report, news decisions are made independently of our board members and financial supporters. Read more about our editorial independence policy here

Creative Commons License

Republish our articles for free, online or in print, under a Creative Commons license.

Join the Conversation

1 Comment

Leave a comment

Welcome to the discussion.

• Transparency. Your full name is required.

• Keep it Clean. Please avoid obscene, vulgar, lewd, racist or sexually-oriented language.

• PLEASE TURN OFF YOUR CAPS LOCK.

• Don't Threaten. Threats of harming another person will not be tolerated.

• Be Truthful. Don't knowingly lie about anyone or anything.

• Be Nice. No racism, sexism or any sort of -ism that is degrading to another person.

• Share with Us. We'd love to hear eyewitness accounts, the history behind an article -- and receive photos, videos of what you see.

• Don’t be a troll. Don’t be a troll.

• Don’t post inflammatory or off-topic messages, or personal attacks.