This Is How Much Each Vaccine Protects Against the Delta Variant, Studies Show

All shots see some reduced effectiveness against the new strain.

On July 6, the Centers for Disease Control and Prevention (CDC) confirmed that Delta had become the dominant COVID-19 variant in the U.S. after estimating it was responsible for 51 percent of cases nationwide. Experts and officials have grown increasingly concerned that areas of the country with low vaccination rates will see surges due to the highly contagious mutated version of the virus circulating among the population. But what about people who've already received their shots? Fortunately, new data has shed light on each vaccine available in the U.S. and how much they protect against the Delta variant.

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According to a study released by Israel's Health Ministry on July 5, the Pfizer vaccine appeared to be somewhat less protective against the Delta variant than other strains, The Wall Street Journal reports. Data collected during an outbreak caused by the strain between June 6 and early July determined that the vaccine's efficacy dropped from 94 percent down to 64 percent effective against COVID infection from the variant.

However, while it may not have stopped the spread of the virus, there was still some good news. Data from the Israeli study also found that the Pfizer vaccine was still 94 percent effective at preventing severe illness during the variant-driven outbreak, only down from 97 percent established in previous studies.

Pfizer wasn't alone in seeing its effectiveness diminished by the new strain. In a June 29 statement released by Moderna, the company announced that while its mRNA COVID vaccine showed promising results against the Delta variant, there was also a drop in the immune response compared to that of the original strain of the virus. Instead, results showed that there was a 2.1-fold reduction in antibody response generated while tackling the latest mutation.

Moderna pointed out that its vaccine still incited an antibody response against all variants it tested against, with all being weaker than the response to the original strain of the virus. Interestingly, the vaccine was actually more effective at producing antibodies against the Delta variant than the Beta variant first identified in South Africa months ago, which saw a six-to-eight-fold reduction in antibodies.

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No studies have yet been performed on the single-dose Johnson & Johnson vaccine and its effectiveness against the Delta variant. However, the company announced in a statement on July 1 that research shows its shot "generated strong, persistent activity against the rapidly spreading Delta variant and other highly prevalent" variants.

"We believe that our vaccine offers durable protection against COVID-19 and elicits neutralizing activity against the Delta variant," Paul Stoffels, MD, Vice Chairman of the Executive Committee and Chief Scientific Officer at Johnson & Johnson, said. "This adds to the robust body of clinical data supporting our single-shot vaccine's ability to protect against multiple variants of concern." According to the statement, both of these studies were submitted to be printed in bioRxiv.

It's worth noting that while a handful of experts have suggested people who got the Johnson & Johnson vaccine consider getting a booster shot of an mRNA vaccine such as Moderna of Pfizer, others believe this would be an unnecessary precaution. During a July 1 White House press briefing, White House COVID adviser Anthony Fauci, MD, vouched for the effectiveness of the one-shot vaccine. "With regard to the idea of boosting, there's a lot of talk about that—but right now, I think we still need to remember that, in fact, the J&J vaccine is a highly effective vaccine that has been recommended very clearly and has received an emergency use authorization," he said.

RELATED: Vaccinated People Who Get COVID Have These 3 Things in Common, Study Shows.

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Zachary Mack
Zach is a freelance writer specializing in beer, wine, food, spirits, and travel. He is based in Manhattan. Read more
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