(NEXSTAR) – News is developing so quickly when it comes to COVID-19 booster shots, it can be hard to keep track of what’s happening. Have they been approved? Am I eligible? When can I get one? The answer to those questions depends on which vaccine you receive originally: Pfizer, Moderna or Johnson & Johnson.

Here’s the status of booster shots for each vaccine type approved in the United States, and the rules that determine who can get one.

Pfizer

Pfizer’s vaccine is the only vaccine type that has emergency use authorization for a booster shot (at publication time). Still, not everyone who got Pfizer is eligible for a third shot at this time.

If you received your second Pfizer shot more than six months ago, you are eligible for a booster shot if you are:

• 65 or older
• 18 or older with a qualifying underlying health condition (like cancer, diabetes, lung disease, and more)
• Work in a high-risk setting where you are more likely to encounter COVID-19 (like first responders, grocery/food workers, public transit workers and more)
• Live in a high-risk setting, like a nursing home

Booster shots could be rolled out to more people in the future, but for now, the Centers for Disease Control says two doses of the Pfizer vaccine is effective at preventing serious illness, hospitalization and death.

Moderna

A panel of outside advisers to the Food and Drug Administration voted unanimously last week to recommend a booster shot of the Moderna vaccine to certain U.S. populations. However, the FDA hasn’t given the booster dose an emergency use authorization (EUA) yet, nor has the CDC weighed in.

Much like the Pfizer booster, the Moderna booster will likely be prioritized for seniors, as well as younger adults with other health problems, jobs or living situations that put them at increased risk from COVID-19. The FDA advisory panel recommended it be administered six months (or more) after the second dose.

For their booster shot, Moderna recipients will likely receive a half-dose of the same vaccine they got for the first and second round.

Moderna said it chose the lower-dose booster because it triggered fewer uncomfortable shot reactions such as fever and achiness and also leaves more vaccine available for the global supply.

Johnson & Johnson

The status of the Johnson & Johnson booster is much like that of Moderna’s; a panel of advisers to the FDA has voted unanimously to approve them, but the FDA still hasn’t voted and the CDC hasn’t taken it up yet.

A key difference here, however, is that all J&J recipients could be eligible – pending FDA approval. Because there are concerns that the one-shot vaccine isn’t as effective at combatting COVID compared to the two-shot varieties, the FDA panel recommended everyone 18 and older be allowed to receive a booster.

The booster could also be administered sooner: at least two months after the original J&J shot.

Ultimately, who will be eligible for the J&J booster and when are both up to the FDA. The panel’s vote is not binding.

The Associated Press contributed to this report.