How long after booster are you fully vaccinated

You may have heard that the Food and Drug Administration (FDA) has granted emergency use authorization to a new pair of COVID-19 booster shots. These updated vaccines are designed to help protect people from the most prevalent subvariants of the current strain: Omicron BA.4 and BA.5.

To learn more about these vaccines, including how they differ from previous COVID-19 booster shots, who is eligible to receive them, and when to schedule them in relation to your flu shot, we checked in with infectious diseases specialist and head of Internal Medicine David Tweardy, M.D.

What are these new COVID-19 boosters, and how do they differ from the existing ones?

Until now, COVID-19 booster shots have been monovalent or univalent. That means they only contained one version of the mRNA sequence for the SARS-CoV-2 virus’ spike protein — the one that came from the original strain which emerged in late 2019 in Wuhan, China.

The boosters that just got approved are considered bivalent vaccines. That means they contain the mRNA sequence for the spike protein of two strains of SARS-CoV-2:

1. the original strain from Wuhan, and
2. the current predominant subvariant of Omicron, BA.5.

The spike protein on the surface of both Omicron’s BA.4 and BA.5 subvariants is exactly the same. So, this booster should protect people against both.

Who is eligible for a bivalent COVID-19 booster shot?

The two vaccines have different age restrictions.

• Moderna: 18 years and older
• Pfizer: 12 years and older

You only need a single booster shot of the bivalent vaccine to be considered fully boosted, but you’re not eligible to get it unless you’ve already been fully vaccinated with either Johnson & Johnson/Janssen’s original one-shot regimen, or Pfizer or Moderna’s original two-shot regimen.

You’re eligible to get a bivalent booster shot two months after you’ve been fully vaccinated.

Can I get a bivalent booster now, if I just recently got my second univalent booster?

No. You’ll need to wait until two months have passed since your last booster shot.

But don’t kick yourself, even if you just got one and now wish you’d waited. The entire point of getting a booster shot is to continue expanding your protection. So, the more boosters you get, the better protection you’ll have.

That’s why I would get a bivalent booster shot as soon as I was eligible.

How long do I need to wait to get the bivalent booster if I’ve had COVID-19?

If you were very ill, you’ll need to wait at least until the worst of your symptoms have resolved, and you have met the criteria to leave isolation. Patients with recent COVID-19 infections also have the option of waiting three months instead of two (counting from the time they first showed symptoms or tested positive) to get a booster shot.

Talk with your doctor to determine the best timing for you to get one if you have any questions.

Are there any special considerations around scheduling, given that it's also time for flu vaccines?

No. The Centers for Disease Control and Prevention (CDC) say there’s still no need to stagger your vaccinations. So, if you’re due for both, you can get your flu shot and your COVID-19 booster at the same time on the same day. You can even get them in the same arm, if you want to cut down on the amount of soreness you experience.

Is there any reason not to mix and match boosters, by getting your bivalent from a different manufacturer than you did the first time?

No. It’s OK to mix and match as long as you’re eligible for the vaccine you prefer.

All of the data that previously showed there were no big differences between those who mixed and matched and those who didn’t still applies. I haven’t seen anything to even imply that anything’s changed.

What about immunocompromised patients? Any special rules for them?

No.

In fact, I am really excited about this latest development, because it could end up being a real game-changer for our immunocompromised patients.

It’s already becoming increasingly rare to die or become really ill from COVID-19. But this bivalent vaccine is another step in the march toward a more endemic stage.

The infrastructure is already in place to make massive quantities of vaccine in a very short time. So, anything after BA.5 could theoretically be added to the composition of the next booster. I think COVID-19 boosters will probably be multivalent from here on out, just like with the flu. And for patients who haven’t been able to mount a sufficient defense against COVID yet, maybe repeated boosters will finally allow them to get there.

Can I get the bivalent booster if I regularly receive EVUSHELD injections to protect myself from COVID-19?

Yes. Those who take EVUSHELD antibody therapy to protect themselves from severe COVID-19 infection can receive the bivalent booster, if eligible. Those who receive a vaccine dose (primary or booster) should wait at least two weeks before getting the EVUSHELD injection, according to the Centers for Disease Control and Prevention’s advisory group.

When might the bivalent boosters be offered to children under 12?

My guess is within three to six months. But it could be faster. Manufacturers are using the exact same processes to make the bivalent boosters as they did to make the originals. So, while the change in proteins included is an important one, it’s still relatively small from the point of view of the body’s developing a new adverse reaction to it. 

I wouldn’t be surprised if the safety and efficacy studies in children under 12 from the original vaccine led to emergency use authorization a bit more quickly with this one than they did with the original. The volume of safety data we have now for the original vaccine may give reviewers more confidence about the safety of the bivalent vaccine, which was generated using the exact same process as the one for the original vaccine.

Where can I find a bivalent COVID-19 booster?

Once bivalent COVID-19 boosters become available, you should be able to obtain one anywhere you’d normally get a COVID-19 vaccination or flu shot.

Will I be able to get the bivalent booster at MD Anderson?

We expect to get bivalent boosters soon. When we do get them, they will only be available for MD Anderson patients and employees. Patients will be able to schedule a booster appointment via MyChart.

Request an appointment at MD Anderson online or by calling 1-877-632-6789.

Health officials are encouraging the public to get vaccinated against the SARS-CoV-2 virus, which causes COVID-19. In addition to an initial course of vaccines, the Centers for Disease Control and Prevention (CDC) provides guidelines for when to get the booster dose.

According to the CDC, people are generally considered fully vaccinated two weeks after their second Pfizer or Moderna mRNA dose or two weeks after their single-dose Johnson & Johnson vaccine. But to build back up any protection that might have waned since your initial vaccination series, it's recommended that everyone who's eligible get a booster. A review published in 2021 in The New England Journal of Medicine found that doing so decreases the likelihood you'll get COVID-19 or become severely ill if you do contract it.

According to the CDC, any fully vaccinated individual older than 16 can get an mRNA booster shot. People who received the Pfizer or Moderna vaccine can receive the booster six months after completing their second dose, and those who initially received the Johnson & Johnson vaccine can get a booster two months after the single-dose vaccine.

While getting boosted is important in stopping the spread of COVID-19, what's not as clear is how soon after that shot someone is considered "fully boosted." Here's what you need to know about how quickly your booster shot will start to work, according to experts.

How the Pfizer COVID-19 Vaccine Works

When you get any vaccine, your immune system mounts an antibody response, which should work to fight off future infection. Say you got your last COVID-19 vaccine several months ago. As time goes on, your immune protection can weaken, and a booster shot re-exposes your immune system, so it makes more antibody-producing cells.

A key factor in this process is a type of white blood cell called memory B cells, which remain in your body "waiting" to recognize and fight off the same pathogen.

"Once you incorporate another jab, your memory B cells can sense the proteins made by the virus; then they start making more antibodies," Pablo Penaloza-MacMaster, PhD, assistant professor of microbiology-immunology at Chicago's Northwestern University Feinberg School of Medicine, told Health.

By the time of your booster shot, your memory B cells have already encountered the viral proteins—either once or twice depending on which vaccine series you initially received. As a result, Penaloza-MacMaster said the cells can create more and better antibodies against COVID-19—which means you'll be more protected if you're exposed to the virus. Penaloza-MacMaster said it's also possible the booster may even offer more cross-protection against different variants.

Johnson & Johnson announced that when people receive its booster two months after the first shot, antibody levels rise by four to six times. Meanwhile, antibody levels are increased 37-fold by Moderna boosters and 25-fold by Pfizer boosters, per reporting from NBC. Research also suggests that mixing and matching vaccines offers just as much—or even more—protection as getting boosted with the same vaccine as you initially did.

It's not possible to know the exact moment when your booster vaccine becomes fully effective. It's unlikely you'd have extra protection the day after you get your booster because it usually takes days or weeks for the memory cells to produce more antibodies. "The only way we could make an estimate is extrapolating how the immune response behaves with other viruses," Penaloza-MacMaster said. "We know between the first and second week you have a massive increase in protection, but there haven't been experiments looking at hours or days."

Infectious disease expert Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, agreed that most people will experience some positive effects from the booster within a week, but the full effect is believed to kick in two weeks after the booster. "In general, that's how the immune system responds and how long it takes to arrive at peak level of protection," Dr. Adalia said.

CDC data that tracked Pfizer vaccine trial participants for 100 days after their boosters suggest that protective effects of the shot may start as soon as seven days after getting boosted. In the trial, people who received Pfizer boosters had a much lower incidence of experiencing symptomatic COVID-19 infections between a week to two months after getting a booster compared to people with just two shots who had received a placebo booster.

While the Pfizer booster showed promising effects, Penaloza-MacMaster said that both mRNA vaccines should start working in similar timeframes, meaning similar results could be expected of the Moderna booster.

The Johnson & Johnson report said that when its booster was given six months after the single shot, antibody levels increased nine-fold one week after the booster. Those antibody levels continued to climb to 12-fold higher a month after the booster. This study was done among people who were boosted six months after their shot as opposed to the recommended two months. (More on getting the vaccine ASAP vs waiting in a bit.)

It's important to keep in mind that a few things can interfere with how effective a booster is, and how much protection a vaccine offers at all. For example, Dr. Adalja said elderly people usually respond less effectively to vaccines, and people on certain immune-suppressing medications may not get the full benefit. "But that's true of any vaccine," Dr. Adaja said.

There's one other factor that can impact the effectiveness of a booster: time between doses. According to Penaloza-MacMaster, the longer the interval between your original vaccine series and the booster dose, the better antibodies your memory cells can create. If you happen to have waited a few extra months before getting your booster, now's the perfect time to get it. That said, Penaloza-MacMaster did not recommend waiting to get a booster in hopes of getting better protection. Now is the best time to get your booster shot if you qualify. "In the middle of a pandemic, we want to get the higher amount of protection right now rather than waiting," Penaloza-MacMaster said.

Thanks for your feedback!