Claim that Pfizer COVID-19 vaccine is not ‘guaranteed’ after 6 months misleads

Wait — Pfizer’s COVID-19 vaccine came with a guarantee?

No. 

And a claim made by conservative commentator Kimberly Klacik suggesting that the vaccine loses all its effectiveness over time is wrong.

Klacik, a Republican who lost her 2020 campaign for a U.S. House seat from Baltimore, made the claim on Instagram, where she has 530,000 followers. She referred to New York City’s requirement to show proof of vaccination to enter some venues, writing:

"So now that it’s been confirmed that the Pfizer vaccine isn’t guaranteed after 6 months, are the bulk of the vaccination cards NYC requires expired? Proving your #COVID vaccination status has become one of the dumbest ideas in US history."

Her post was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Facebook.)

Let’s first dismiss the notion that advocates of vaccination say that COVID-19 vaccines come with any guarantee.

"COVID-19 vaccines are effective and are a critical tool to bring the pandemic under control; however, no vaccine is 100% effective at preventing illness," the federal Centers for Disease Control and Prevention says. "Some fully vaccinated people will get sick, and some will even be hospitalized or die from COVID-19."

Now let’s get to how the Pfizer vaccine loses some, but not all, effectiveness over time.

When we asked Klacik to back up her statement, she said multiple reports, including a Reuters news story, stated that the vaccine "loses its effectiveness after six months."

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stated on November 26, 2024 in an Instagram post

“The CDC says that little 6 month old babies must get SEVEN doses of the Covid vaccine in order to be considered fully ‘up to date’ on their vaccinations.”

The Reuters story said the vaccine’s effectiveness drops after six months.

The study, funded by Pfizer and peer reviewed, was published Oct. 4 in The Lancet, a British medical journal. Researchers led by an epidemiologist at Kaiser Permanente Southern California health care system studied the Pfizer vaccine’s effectiveness. They analyzed the electronic health records of more than 3 million patients ages 12 and up in the system, from Dec. 14, 2020, to Aug. 8, 2021. The study was designed to assess the effectiveness of the vaccine against infection and hospitalizations for up to six months.

Key findings: 

• The vaccine is 90% effective against hospital admissions for up to six months, at least. 

• Effectiveness against infection dropped from 88% to 47% after five months. Waning effectiveness was expected, the study said, based on other studies.

• Reduction in vaccine effectiveness against infections over time "is probably primarily due to waning immunity with time, rather than the delta variant escaping vaccine protection."

• This and other studies "suggest that booster doses are likely to be needed to restore the initial high amounts of protection observed early in the vaccination program."

• The study underscores "the importance of continuing to prioritize improving COVID-19 vaccination rates, including in hard-to-reach communities."

Klacik said "it's been confirmed that the Pfizer" COVID-19 "vaccine isn't guaranteed after six months" and suggested it loses all effectiveness.

The vaccine never came with any guarantee. 

Klacik’s claim alludes to a study that found that the Pfizer vaccine’s effectiveness in preventing infection dropped from 88% to 47% after five months. In preventing hospital admission, the vaccine remained 90% effective over six months, the study found. 

The claim contains only an element of truth. We rate it Mostly False.