ALBANY, N.Y. (NEWS10)- People who were fully vaccinated with the Pfizer COVID vaccine can get a booster shot as of September 22. Those who got Moderna or Johnson & Johnson’s (J&J) vaccine must wait to see if the Food and Drug Administration (FDA) will authorize one.

The FDA will be discussing the possibility of a Moderna booster on Thursday, and a J&J booster on Friday. They’ll be considering boosters for both shots for fully vaccinated people who are 18 or older.

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

When it comes down to dosing, there is no difference between all available COVID vaccines. Pfizer’s initial vaccination series is administered in two 0.3 milliliter doses. It’s the same for the Pfizer booster and/or third doses—0.3 milliliters, according to the FDA.

“There is no difference between the additional, or third doses, and booster shots. The only difference is who may qualify to receive them,” the CDC said when News10 reached out to them.

Although boosters haven’t been authorized yet, Moderna’s two-shot series—as well as the booster and third dose—are all administered in 50 microgram doses, according to Moderna and the FDA. J&J’s initial shot is 0.5 milliliters and its booster or second dose is also 0.5 milliliters, the FDA and J&J said.

Third doses of Pfizer and Moderna have been approved for people with a compromised immune system. This includes organ or stem cell transplant recipients, people getting cancer treatment, and/or other conditions that can affect a person’s immunity, according to the Centers for Disease Control and Prevention (CDC).

If the dosing remains the same for either boosters or third doses, then what is the actual difference? According to Daniella Rodrigues, Supervisor of Inpatient Pharmacy and Director of the Pharmacy Residency Program at Saint Peter’s Health Partners, it comes down to intent.

If the intent is to help someone who has a compromised immune system obtain the same level of protection as someone with a normal immune system, it would be considered a third dose. A booster is intended to boost someone’s immune response because immunity wanes over time, Rodrigues said.

There’s also the length of time between the initial two-shot series and the booster or third dose. A booster should be administered approximately six months from the last dose. A third dose can be administered 28 days after the last dose, she said.

The Pfizer booster was approved for:

  • People 65+ years old
  • People 18-64 years old who are at high risk of developing severe COVID (includes people with underlying health conditions)
  • People 18-64 years old who may come in contact with COVID frequently, putting them at a higher risk of having a severe case (includes teachers, jail/prison staff, health care, or grocery store workers)

The FDA said people should wait at least six months after their last dose to get a booster shot. The Biden Administration recommended people get a booster shot at around eight months. In a joint statement, experts from the U.S. Department of Health and Human Services said:

“Based on our latest assessment, the current protection against severe disease, hospitalization, and death could diminish in the months ahead, especially among those who are at higher risk or were vaccinated during the earlier phases of the vaccination rollout. For that reason, we conclude that a booster shot will be needed to maximize vaccine-induced protection and prolong its durability.”

It’s important to note that—although the FDA doesn’t make it very clear in its September 22 press release authorizing a Pfizer booster shot—the CDC said the booster is for people who initially received the Pfizer vaccine:

The Advisory Committee on Immunization Practices (ACIP) and CDC’s recommendations are bound by what the U.S. Food and Drug Administration’s (FDA) authorization allows. At this time, the Pfizer-BioNTech booster authorization only applies to people whose primary series was Pfizer-BioNTech vaccine. People in the recommended groups who got the Moderna or J&J/Janssen vaccine may need a booster shot. More data on the effectiveness and safety of Moderna and J&J/Janssen booster shots are expected soon. With those data in hand, CDC will keep the public informed with a timely plan for Moderna and J&J/Janssen booster shots.


If someone is not eligible for a booster shot, they may still be eligible for a third dose if they are immune-compromised. According to the CDC third doses should be considered for:

  • People receiving active cancer treatment for tumors or cancers of the blood
  • People who have had an organ transplant and are taking medicine to suppress their immune system
  • People who have had a stem cell transplant within the last two years or are taking medicine to suppress their immune system
  • People with moderate or severe primary immunodeficiency (that is, people with DiGeorge syndrome or Wiskott-Aldrich syndrome)
  • People with advanced or untreated HIV infection
  • People receiving treatment with high-dose corticosteroids or other drugs that may suppress their immune response