Note: Pfizer COVID vaccine booster shots are now available for certain eligible groups. Find out who can get a Pfizer booster shot, and how to make an appointment near you.

You're not imagining it.

Back in mid-August, U.S. health officials announced plans to offer COVID-19 booster shots to all Americans, starting as early as this week (Sept. 20).

That hasn't happened.

And while the Food and Drug Administration has now authorized a booster dose of the Pfizer-BioNTech coronavirus vaccine for people age 65 and older and certain other groups, with endorsement from the CDC, you could be forgiven for wondering: What happened to this previous timeline? When could we actually see booster shots roll out? And who might get them first?

I thought booster shots for all were starting Sept. 20? What changed?

The original White House booster plan for the general public, announced on Aug. 18, called for an extra dose eight months after getting the second shot of the Pfizer or Moderna vaccines. (That time frame was since revised to six months.) The one-shot Johnson & Johnson vaccine was not included in the plan.

But in the last several weeks since the Biden administration's announcement, a lot has changed. According to The New York Times, the projected September time frame "set off alarm bells" among officials in the FDA.

Earlier this month, top federal health officials allegedly warned the White House that it should scale back its booster-shot plan, the NY Times reported. Representatives from the FDA and the Centers for Disease Control and Prevention purportedly told the Biden administration they would need more time to review all the available data.

COVID-19 vaccine manufacturers have been conducting their own research into the efficacy of booster shots for their particular vaccines. The next stage on the road to booster-shot approval for any particular manufacturer is a review by an advisory panel of experts convened by the FDA. This panel is a part of the FDA's overall evaluation of the safety and effectiveness of a third dose, which is also being reviewed by a CDC advisory panel.

But now we have one approved vaccine booster, right?

Yes. On Sept. 22, the FDA authorized a booster dose of the Pfizer COVID-19 vaccine. But this booster shot only applies to people who have gotten the Pfizer vaccine for their first two shots, and who:

• Are 65 and older
• Are at high risk of experiencing severe COVID-19 symptoms
• Have jobs or institutional exposure to the virus that puts them at high risk of contracting COVID-19

The FDA says that a third shot can be given at least six months after completion of a person's last Pfizer shot. On Sept. 24, the CDC formally signed off on the plan.

This means these eligible groups will be able to get their Pfizer booster shot in California soon. The Western States Scientific Safety Review Workgroup — which represents California, Nevada, Washington and Oregon — will now independently review the FDA and CDC recommendations, and only then can any of the coronavirus vaccine boosters be distributed in California.

This FDA authorization comes after the organization's advisory panel met Sept. 17 and voted 16-2 against a plan to use Pfizer boosters for people 16 and older. The same experts did, however, vote 18-0 in support of the FDA authorizing a booster for people 65 and older or at high risk of severe COVID-19. The FDA typically follows the advice of its advisory committees — although they're not required to.

On Sept. 23, the CDC's own advisory panel met to make specific recommendations about use of this Pfizer booster. The CDC panel aligned with the FDA authorization in all respects, except for disagreeing with the FDA on the question of people whose jobs are more likely to expose them to COVID, such as health care workers and teachers.

The committee said that these people should not yet be allowed to receive an extra Pfizer dose, but stressed that its recommendations could change if new evidence shows more people need a booster. But CDC Director Dr. Rochelle Walensky ultimately chose not to follow the advisory panel's judgement on the issue of boosters and high-risk jobs.

How did the thinking on booster shots change?

Even before the FDA's advisory panel delivered their judgement on the Pfizer vaccine, the FDA's own scientists were expressing their skepticism about the need for booster shots.

They said that "data indicates that currently US-licensed or authorized COVID-19 vaccines still afford protection against severe COVID-19 disease and death in the United States." As Matthew Herper and Helen Branswell wrote for STAT, an online publication covering health, medicine and scientific discovery news:

"On one side are drug companies and some researchers, who point to data showing the efficacy of the vaccines to protect all infections is waning and that a third shot will provide additional protection.

"On the other are those who point out that these vaccines are still keeping people out of the hospital and preventing them from dying, indicating that a booster is not needed yet."

Remember, the FDA panel's vote specifically related to whether a third shot of the Pfizer vaccine is necessary for most people. In voting against the plan, the panel was not saying the vaccine itself is unsafe, and was certainly not trying to cast any doubt on the general efficacy of the vaccines.

To reiterate, yet again, the COVID-19 vaccines work! And while breakthrough cases in vaccinated people do happen, the vaccines vastly reduce the risk of hospitalization or death. If you haven't got your first shots yet, here's how to find a COVID-19 vaccine near you.

Does this mean boosters won't happen for the general public at all?

We just don't know right now.

On Monday, the White House's chief medical adviser, Dr. Anthony Fauci, told NPR that he expected more data to become available in the next few weeks that would "actually modify and expand the recommendation" for the use of boosters to more people. "But for now we'll go with what the FDA advisory committee has recommended," Fauci said.

Fauci said last week that an FDA review of the Moderna and J&J vaccines was "a few weeks away."

One of the latest booster-related developments is the release of data from Johnson & Johnson on its own COVID-19 vaccine booster shot. Trials show that people who receive a J&J booster shot are better protected against the coronavirus for a longer period of time than those who just get one shot, according to the company.

On Sept. 22, a panel of advisers to the CDC met to discuss the question of who should be offered a COVID-19 booster. This panel, officially known as the CDC’s Advisory Committee on Immunization Practices (ACIP), considered implementing a more limited booster initiative specifically targeting older populations or people whose jobs put them at higher risk of catching or spreading the virus — like front-line health care workers.

Some members of the CDC panel also questioned whether the existing data sufficiently demonstrated the need for booster shots at all, and advocated for postponing any such booster plans until more evidence was available.

How quickly might booster shots be more broadly available?

Again, whether it's Pfizer, Moderna or J&J, any COVID-19 vaccine has to first be reviewed by the FDA's advisory panel and decide whether or not to authorize a booster. This is the process that has now resulted in the FDA's authorization of the Pfizer vaccine for certain groups.

After that, and a similar CDC review process, the Western States Scientific Safety Review Workgroup — which represents California, Nevada, Washington and Oregon — independently reviews the agencies' recommendations. Only then can any of the COVID-19 vaccine boosters be distributed in California.

But even setting aside the time frame needed for the FDA and the CDC to review all the available data, be aware that scheduling a third shot could be more confounding, in certain ways, than the process of getting the initial ones.

Remember that the Biden administration's revised goal was to get booster shots in people's arms six months after receiving their last COVID-19 vaccinations. But because the COVID-19 vaccines rolled out at different times for different groups of people — in California and elsewhere — everyone would then have a different date for receiving their potential third shot based on when they got their previous one.

There's also the matter of which COVID-19 vaccine you originally got. As we're seeing, the process of Pfizer, Moderna and J&J releasing their own trial results — which are then reviewed by FDA and CDC advisory panels — is not a coordinated one. So there's the possibility that booster shots could be available for one type of COVID-19 vaccine well before another.

In addition, the FDA's choice to follow its advisory panel's endorsement of the Pfizer COVID-19 vaccine for people 65 and older, or those at elevated risk — as opposed to the general public — is a strong indication we'll see a booster rollout that's staggered based on eligibility. And that will likely require complex logistical planning and accessibility considerations.

Even before the FDA panel's specific recommendation last week on eligibility, San Francisco Department of Public Health officials said they were already anticipating "a phased rollout similar to how the vaccine was initially distributed: prioritizing the most vulnerable, in collaboration with our health care and pharmacy partners."

Amid all this is also the ethical issue of Americans getting third shots of the COVID-19 vaccine while so many other people around the world have been unable to access even their first one.

Top scientists at the World Health Organization met the White House's August announcement on booster shots with bitter objections. "We're planning to hand out extra life jackets to people who already have life jackets, while we're leaving other people to drown without a single life jacket," said Dr. Michael Ryan, executive director of the WHO's emergencies program.

Aren't third shots already available for some people?

Immunocompromised people who already got two doses of the Pfizer or Moderna vaccine can now get a third shot to boost their protection from COVID-19. This is a separate initiative that predates the Biden administration's proposal on offering booster shots more broadly.

Right now, only a very small group of people with compromised immune systems qualify for this third dose — many serious conditions, like diabetes or heart disease, are not currently included. Read the CDC's list clarifying exactly who is eligible.

If you do qualify for a booster shot, we have more information on how to make your appointment, plus information that immunocompromised people considering the third shot may wish to consider.