Here’s How Long Your COVID Vaccine Booster Provides Protection


Less than half of fully vaccinated Americans have received a third shot. 

Sarah Tew/CNET For the most up-to-date news and information about the coronavirus pandemic, visit the WHO and CDC websites.

As COVID vaccines demonstrate decreased protection over time, global health officials are considering a second booster shot for the general population. The US Food and Drug Administration is potentially preparing to authorize a fourth vaccine dose in fall 2022, The Wall Street Journal reported Saturday.

“The potential future requirement for an additional boost — a fourth shot for mRNA or a third shot for Johnson & Johnson — is being very carefully monitored in real time,” White House Chief Medical Adviser Dr. Anthony Fauci said in a press briefing last week. 

Messenger RNA vaccines, like the ones offered by Pfizer and Moderna, offer good protection against serious COVID-19 complications — especially after a booster — but their potency wanes over time.

In its latest weekly update, the US Centers for Disease Control and Prevention reported that protection against hospitalization from mRNA vaccines dropped noticeably after just four months, even with a booster: When the delta variant was predominant, protection against hospitalization was 96% within two months of a third mRNA shot, but sank to 76% within four months.

During the omicron wave, protection from hospitalization fell from 91% within two months of an mRNA booster to 78% after four months.

Read on to learn what we know about how vaccines remain effective and when a fourth shot could be approved.

For more, read everything we know about long COVID, learn why you shouldn’t just “get COVID over with,” and get the latest on shifting vaccine requirements across the US.

How long do mRNA vaccines remain effective against COVID-19?

How long your vaccine remains effective depends on the strain of COVID you’ve been exposed to, how many shots you’ve received and what you’re trying to prevent.

The effectiveness of COVID-19 vaccines decreases over time, especially against potent strains like the omicron variant. One December study from the UK’s Health Security Agency indicated protection from infection waned as much as 65% after just 10 weeks.

A metastudy published in The Lancet journal on Feb. 21 determined that mRNA vaccines’ efficacy against infection decreased by 20 to 30% six months after the third shot, though their protection against “severe” disease remained high in the same time frame, 

For symptomatic COVID-19 disease, vaccine effectiveness decreased by roughly 25% across the board at the six-month mark, and by 32% in people age 50 and older.

The February CDC study found vaccines’ protection against hospitalization when omicron was dominant dropped from a high of 91% within two months of a booster to 78% after four months.

Protection from an ER visit slipped from 87% within two months of a booster to just 66% after four or five months. After another five months, it plummeted to just 31% protection against an ER or urgent-care encounter.

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Three shots of an mRNA vaccine provided 87% protection against an ER visit within the two months, but fell to 66% after four months, and 31% after nine.

Getty Images

Without a third booster, Pfizer/BioNTech’s vaccine, Comirnaty, was 88% effective several weeks after the second dose, but only 47% six months later, according to an October 2021 Lancet article, Reuters reported. 

Its ability to fend off hospitalization and death remained high at 90% in the same time period.

Does new data suggest a fourth shot is coming soon? 

The CDC updated its guidance in January to indicate that immunocompromised people could receive a fourth COVID-19 shot. Israel has already approved a fourth dose of Pfizer or Moderna’s mRNA vaccine for vulnerable people 18 and older. Sweden has also authorized citizens over 80 to get a fourth shot, starting Feb. 22.

Throughout the omicron wave, Fauci has stressed the importance of thoroughly evaluating the data on third booster shots before making a decision on a fourth dose. In a January interview, he said, “before we make that decision about yet again another boost, we want to determine clearly what the durability of protection is of that regular boost, that third shot that we’re talking about.”

As more data on booster protection indicates waning protection, the FDA is making decisions on who will be eligible for a fourth shot, when those additional boosters will be offered and whether the extra shot will be specific to omicron.

According to the Wall Street Journal, regulators are leaning toward a fall 2022 authorization of additional mRNA vaccine boosters. One idea is to synchronize the new COVID shots with the timing of the existing yearly influenza vaccine in order to increase takeup.

Who is eligible for a fourth vaccine shot right now in the US?

In October, the CDC approved a third primary shot of an mRNA vaccine, like Pfizer’s or Moderna’s, for individuals who are immunocompromised or have other specific health issues. The third shot should be delivered at least 28 days after the second.

Five months after that third primary shot, vulnerable people are eligible for their booster, or fourth shot.

Conditions that the CDC considers “moderately or severely immunocompromised” include:

  • Patients in active cancer treatment for tumors or blood cancers
  • Those with organ transplants who take medicine to suppress the immune system
  • Those who’ve received a stem cell transplant within the last two years
  • Moderate or severe immunodeficiency (such as DiGeorge syndrome, Wiskott-Aldrich syndrome)
  • Serious HIV infection
  • Patients taking medicine or drugs that may suppress their immune response

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Immunocompromised people have reported seeking fourth shots but being turned away by some pharmacies. Kaiser Health News reported the CDC spoke with major pharmacy chains to ensure they are aware of the eligibility of some Americans to receive their fourth shot.

According to the CDC’s recommendations, patients do not need to show proof that they are immunocompromised.

Will everyone be eligible for a fourth COVID vaccine dose eventually?

Scientists in Germany, the UK and other countries are considering fourth shots of a COVID-19 vaccine for the general public. In January, health ministers in European Union countries were told to prepare for fourth doses as soon as data indicates they are needed, Reuters reported.

This year, Israel started offering fourth booster shots to citizens 60 and older before expanding to all vulnerable adults, and Denmark authorized fourth doses for at-risk communities. Sweden recently authorized fourth doses of the mRNA vaccines for all citizens over 80, starting Feb. 22.

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Pfizer Chief Scientific Officer Mikael Dolsten, seen here in 2017, says a fourth vaccine dose is “very likely.” 

Sylvain Gaboury/Patrick McMullan/Getty Images

“With the data now coming for the omicron variant, it is very clear our vaccine for the omicron variant should be a three-dose vaccine,” Ugur Sahin, CEO of BioNTech, which makes a vaccine in partnership with Pfizer, said in a statement. 

If three doses of the Pfizer COVID-19 vaccine are needed to protect against omicron, the timeline for a fourth shot could be pushed up to as early as March, Pfizer executives said.

“I think it is very likely that we will need a fourth booster, possibly already this spring, particularly if omicron continues to dominate,” Mikael Dolsten, Pfizer’s chief scientific officer, told CBS News.

What has Pfizer said about a fourth booster shot to protect against COVID-19? 

“I think we will need the fourth dose,” Pfizer CEO Albert Bourla told CNBC in December. Bourla initially projected a waiting period of a full year after a third dose but, with omicron, “we may need it faster,” he said.

“There are vaccines like polio [where] one dose is enough,” Bourla said back in April. “And there are vaccines, like flu, that you need every year. The COVID-19 virus looks more like the influenza virus than the poliovirus.”

Executives said the companies are experimenting with an omicron-specific version of Pfizer-BioNTech’s current vaccine, Comirnaty, that could be ready by March, pending regulatory approval.

They’re also looking at a multivariate vaccine that could protect against other strains, such the original alpha variant and more virulent delta strain.

Getting vaccine shotGetting vaccine shot

Health officials are increasingly leaning toward a fourth COVID-19 booster shot, potentially in fall 2022.

Monty Rakusen

What has Moderna said about a fourth shot?

Like Pfizer, Moderna said it’s testing the effectiveness of its COVID-19 vaccine, SpikeVax, against omicron. The company has offered little specifics but said a variant-specific shot could be available in early 2022.

Moderna President Stephen Hoge said we’ll most likely need seasonal COVID boosters, much like we do with the flu, at least to protect against the highest risk of infection and serious illness. Moderna is working on omicron-specific boosters, Hoge told Reuters, but realistically they won’t be on the market “before March [2022] and maybe more in the second quarter.” 

Its current booster is a 50-microgram dose, and while the company has also reported a 100-microgram dose of Spikevax has proven exponentially effective against omicron, it does not plan to seek approval from the FDA for the double-dose. 

What has Johnson & Johnson said about a second booster shot? 

A study of 69,000 health care workers released in December by the South African Medical Research Council found that, for those who already received the J&J vaccine, Ad26.COV.2, a booster given six to nine months later raised their odds against hospitalization from 63% to 85%.

The research was conducted between mid-November and mid-December 2021, when the omicron variant represented 98% of all confirmed COVID cases in South Africa, suggesting the vaccine offers strong protection against the highly contagious strain.

“This adds to our growing body of evidence which shows that the effectiveness of the Johnson & Johnson COVID-19 vaccine remains strong and stable over time, including against circulating variants such as omicron and delta,” Dr. Mathai Mammen, global head of Janssen Research & Development, a pharmaceutical subsidiary of Johnson & Johnson, said in a statement.

For more on COVID-19, here’s how the new omicron variant is different from the delta strain, what to know about the Moderna COVID booster and how to choose which booster shot to get.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.

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