Do I need a COVID vaccine booster shot for my Pfizer, Moderna or Johnson & Johnson vaccine?

• UPDATE: Johnson & Johnson says its booster vaccine offers a ninefold increase in antibodies

The U.S. will begin offering COVID-19 booster shots this fall for all Americans who received the Pfizer-BioNTech or Moderna vaccines, eight months after their second shot, beginning Sept. 20, pending authorization from the U.S. Food and Drug Administration.

"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," the statement from the Department of Health and Human Services and other administration medical experts said. "For that reason, we conclude that a booster shot will be needed to maximize vaccine-induced protection and prolong its durability."

What does this mean? We've got answers.

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Do I need a COVID booster shot?

You almost certainly will.  

Data published by Israel’s Ministry of Health shows that protection from the Pfizer/BioNTech vaccine dropped off precipitously after six months, from 95% down to 40-50% effectiveness against infection, said Dr. Eric Topol, vice president for research at Scripps Research in La Jolla, California, and a national expert on the use of data in medical research. The vaccine was still highly protective against serious illness and death, but not against milder COVID-19.

“There’s still a risk for long COVID and people can get quite ill from symptomatic infections, you can’t gloss over that,” he said.

But availability for booster shots will be staggered, with immunocompromised people getting it now and everyone else later.

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Who can get a COVID booster shot?

Right now, only people who have lowered or compromised immune systems can get a third COVID shot of the Pfizer or Moderna vaccine.

But soon, everyone will be recommended to get one. The initial doses will go to the first people who were fully vaccinated, which means health care providers, first responders, nursing home residents and other seniors.

According to the statement, the administration plans to deliver booster shots directly to residents of long-term facilities.

Why are immunocompromised people getting third COVID shots now?

The FDA determined that transplant recipients and others with a similar level of compromised immunity can receive a third dose of the vaccines from Pfizer and Moderna at least 28 days after getting their second shot. 

People who are immunocompromised may not have gotten adequate protection from their earlier doses of COVID-19 vaccine and are more likely to mount a response to an additional dose, the Food and Drug Administration determined.

"With the second dose of two-dose regimens with the mRNA vaccines, people with normal immune systems not only have an antibody response, but it's off the charts," said Dr. Dorry Segev, Associate Vice Chair for Research and Professor of Surgery at Johns Hopkins School of Medicine. "And, still, half of transplant patients have no antibody response at all. In those who do have an antibody response, in general, the levels are much lower than those in people with normal immune systems."

Segey and his colleagues tested data from more than 18,000 fully-vaccinated recipients of large organs such as lungs or kidneys across the United States and found that 151 of them caught the virus. Of those, more than half were hospitalized with COVID symptoms and roughly one in 10 died.

That rate on infection, while still low, is 82 times higher than in people with normal immune systems, and the rate of serious illness was 485 times higher.

I'm not immunocompromised. Why can't I get an additional COVID vaccine shot right now?

For about 97% of vaccinated Americans, you don't need it yet.

Vaccinated people with healthy immune systems are still well-protected and should not be getting another shot just yet.

Studies have found the three vaccines available in the United States – Moderna, Pfizer-BioNTech and Johnson & Johnson – all remain effective against the delta variant, although reports are starting to come in of a drop-off in effectiveness after time.

"The vaccine is effective at preventing severe illness regardless of what the strain is," said Dr. David Hirschwerk, an infectious disease specialist at Northwell Health in Manhasset, New York.

It is far more important to get unvaccinated people vaccinated, and for people who have only received one of the two required doses of the Pfizer or Moderna vaccines to get their second dose. The best defense for immunocompromised people is to be surrounded by people who are vaccinated.

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If you've had an organ transplant, if you're undergoing cancer treatment, if you're a dialysis patient, if you have HIV, if you have inherited diseases that affect the immune system (e.g., congenital agammaglobulinemia, congenital IgA deficiency) or are otherwise immunocompromised and you have received both shots of an mRNA vaccine such as Moderna or Pfizer-BioNTech, you may need an additional shot soon.

There are roughly 9-10 million Americans who are immunocompromised, about 2.7% of adults in the United States, according to the U.S. Centers for Disease Control and Prevention (CDC). 

A study by Johns Hopkins researchers found that after one dose of the vaccine, 100% of the people with normal immune systems will produce some detectable antibodies against COVID but only 20% of transplant patients do.

"With the second dose of two-dose regimens with the mRNA vaccines, people with normal immune systems not only have an antibody response, but it's off the charts," said Dr. Dorry Segev, Associate Vice Chair for Research and Professor of Surgery at Johns Hopkins School of Medicine. "And, still, half of transplant patients have no antibody response at all. In those who do have an antibody response, in general, the levels are much lower than those in people with normal immune systems."

Segey and his colleagues tested data from more than 18,000 fully-vaccinated recipients of large organs such as lungs or kidneys across the United States and found that 151 of them caught the virus. Of those, more than half were hospitalized with COVID symptoms and roughly one in 10 died.

That rate on infection, while still low, is 82 times higher than in people with normal immune systems, and the rate of serious illness was 485 times higher.

Not only are they more vulnerable, people with immunocompromised immune systems may act as petri dishes where new and more dangerous coronavirus variants can develop. As a study in the New England Journal of Medicine confirmed, that makes immunizing them and protecting them from infections even more important.

What is a COVID booster shot?

What the FDA has authorized and the CDC has recommended to date is simply a third shot of the Pfizer or Moderna vaccine.

Pfizer is currently testing a booster shot designed to work more effectively against the delta variant.

Will there be COVID booster shots for people who got the Johnson & Johnson vaccine?

Officials said that booster shots will likely also be needed for people who received the single-dose Johnson & Johnson shot, but said the federal rollout of the J&J vaccine didn't start in the U.S. until March and they're still collecting data on its continuing effectiveness.

Johnson & Johnson reported August 25 that studies show a booster shot of their vaccine offered a ninefold increase of antibodies compared with the vaccine on its own. The company said it was working with federal officials, including the Food and Drug Administration and Centers for Disease Control and Prevention, on next steps to boost the effects of the vaccine and ready a possible booster shot. 

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Do immunocompromised people who got the Johnson & Johnson vaccine get a second shot?

There has been no authorization yet for additional shots for the immune-compromised patients who received the Johnson & Johnson vaccine.

I got the J&J vaccine. Should I get a shot of Pfizer or Moderna to be safe?

The CDC's official position is to strongly advise everyone not to mix your vaccines, they're not interchangeable (although the latest recommendation does say if you got Modena or Pfizer the first two times but can't now, you can get the other).

This doesn't mean it's unsafe, only that it hasn't been adequately tested yet, which means there is no federal authorization to try it.

"Johnson & Johnson is not a bad vaccine – it’s way better than getting nothing," said Dr. Otto Yang, an infectious disease specialist at UCLA Health. "But it’s not as good as other options."

A large-scale trial of the J&J's vaccine showed it was effective against COVID-19, preventing more than 70% of symptomatic infections and about 86% of serious ones. According to Johnson & Johnson their vaccine's protection lasts against all variants now circulating for at least eight months.

If you're concerned about the effectiveness of your vaccine, your best bet for now is to continue social distancing and wearing masks in public indoor places, especially if you are immunocompromised or have immunocompromised people in your household or circle of friends.

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How do I get a third COVID shot?

Some locations are already offering them. Publix now allows you to sign up for additional Pfizer or Moderna shots on their website or through their walk-in service, although Pfizer shots are only available in Brevard, Duval, Orange, and Polk counties as of August 15.

CVS also has added an option for immunocompromised people to get a third shot.

Walmart has added a FAQ page just for the 3rd dose. They're available for walk-ins.

Third shots are currently only available for people who meet the CDC's requirements for immunocompromised people. You must have taken your second dose a minimum of 28 days before getting a third shot. 

Third shots also may be available at other clinics or pharmacies, check your local locations.

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How often will COVID booster shots be needed?

The initial recommendation for booster shots is eight months, according to the statement from the administration, but this may change in the future.

Researchers are still figuring out the best way to measure whether someone has enough protection. The level of antibodies that fight this infection are important but there are other factors, such as T cells, which are hard to measure. Someone might have few neutralizing antibodies but enough T cells to prevent severe infection. 

The current expectation is that protection may begin to fade between 6-12 months. But the vaccines still seem to be working well in preventing serious disease and the vast majority of hospitalized patients are unvaccinated.

People also appear to lose protection at different rates. The immune system weakens with age, and the antibody response to COVID-19 vaccination is believed to fall off substantially around 80, though it may be younger among minority populations, said Dr. Maria Torroella Carney, an internist and geriatrician at New York-based Northwell Health.

Why do mRNA vaccines like Pfizer lose effectiveness over time?

Unknown, so far. 

Topol believes it may be due to the short dosing schedule the United States chose, based on the information available at the time: three weeks apart for Pfizer and four weeks for Moderna. 

“This might not have happened if the spacing had been eight to 12 weeks. That’s what Canada, the United Kingdom and Scotland did,” Topol said.

"We just picked out two because we needed to move our butts to get a vaccine out there," Fauci said. "The idea that you only need two shots per vaccine was just a decision made out of the urgency of the situation."

Different pathogens require a different number of shots to provide long-term protection, with people getting three hepatitis shots, for instance, and four or five against the measles. 

The companies are also updating their vaccine, called BNT162b2, to directly address the delta variant. They are currently producing material for a clinical trial, which they expect to begin in August, pending regulatory approvals.

Contributors: Elizabeth Weise, Karen Weintraub, Courtney Subramanian, USAT TODAY Network

C. A. Bridges is a Digital Producer for the USA TODAY Network. Follow him on Twitter at @cabridges