‘Wake-up call’: New Mayo Clinic study shows Pfizer vaccine may only be 42% effective against Delta variant, Moderna 76%

A new preprint study has shown that both the Pfizer and Moderna coronavirus vaccines are much less effective against the fast-spreading Delta variant, a fact a White House official has said is a wake-up call.

The Mayo Clinic study showed that the Pfizer vaccine was only 42% effective against Covid-19 in July, a month when health officials repeatedly warned the public that the Delta variant was more transmittable and leading to rapid rises in cases.

The Moderna vaccine, on the other hand, was found to be 76% effective in protecting from the virus that same month. 

Those numbers are fairly significant drop-offs from the rest of the year. Comparing the effectiveness of the Moderna and Pfizer vaccines from January to July, their overall efficacy was 86% and 76%, respectively. 

In terms of hospitalizations, both were more reliable, with Moderna being 92% effective at preventing severe cases requiring hospitalization from coronavirus, while Pfizer was 85% effective.

Comparing numbers from multiple states, including Florida and Minnesota, the data consistently showed that Moderna likely presents less of a risk of a breakthrough infection. 

Venky Soundararajan, a lead author of the study, said that the results show that both the stronger Delta variant and a reduction in long-term effectiveness are “both factors” behind the lower numbers. 

“The Moderna vaccine is likely – very likely – more effective than the Pfizer vaccine in areas where Delta is the dominant strain, and the Pfizer vaccine appears to have a lower durability of effectiveness,” Soundararajan said, according to Axios. 

The new study has yet to be peer reviewed, but the team behind the research is already reportedly working on a followup study that will more specifically look at the durability of the vaccines against the Delta variant. 

The surprising study trended on social media on Thursday, with many people expressing shock, using the results to question the effectiveness of the vaccines and suggesting acquiring “natural immunity” was a better option.

Even officials in President Joe Biden’s administration are reportedly worried about the study. One unidentified “senior Biden official” told Axios the results are a wake-up call.

“If that's not a wakeup call, I don't know what is,” they said. 

Concerns about the long-term effectiveness of coronavirus vaccines have mounted in recent weeks as health officials have repeatedly warned about a potential surge of cases in the fall. 

White House medical advisor Dr. Anthony Fauci has said booster shots will likely be required for the already vaccinated soon enough.

“It’s likely that that will happen at some time in the future,” Fauci told ‘CBS This Morning’ on Thursday. “We’re already starting to see indications in some sectors about a diminution over time, that’s durability.”

He added that booster shots will likely only be needed in the short-term future for the “immune compromised.”

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