Dr Fauci DISMISSES Mayo Clinic study that claims Pfizer COVID vaccine is only 42% effective at preventing Delta variant infection while Moderna is 76% as he says both should be used as booster shots

Dr Anthony Fauci has dismissed a preliminary study whose findings suggest a Moderna shot is more effective at preventing a COVID Delta infection than a Pfizer one.

Asked about the study - done by biotech firm nfrence, which is based at the prestigious Mayo Clinic and Cambridge, Massachusetts, the White House COVID tsar said: 'That study … is a pre-print study, it hasn't been fully peer-reviewed.'

Speaking on CBS's Face the Nation, Fauci added: 'I don't doubt what they're seeing, but there are a lot of confounding variables in there, about when one was started, the relative amount of people in that cohort who were Delta vs Alpha – right now, if we get boosters … it's clear we want to make sure we get people, if possible, to get the boost from the original vaccine.' 

The study was shared on medrvix last week - a site which publishes preliminary findings, before they have been peer-reviewed and rubber stamped.

Dr Anthony Fauci, pictured in July, has urged caution on claims Moderna's COVID vaccine offers better protection against the Delta variant than Pfizers 

Researchers from the Mayo Clinic in Rochester, Minnesota, found that the Pfizer-BioNTech vaccine - the most commonly used shot in the U.S. - was only 42 percent effective against infection, while the Moderna vaccine was only 76 percent effective in July.

For the study, published on pre-printer server medRxiv.org - meaning it has not yet been peer review - the team gathered data on more than 25,000 Minnesotans from January to July. 

While the vaccines remained about as effective as advertised, around 90 percent, for the first six months of the year, their effectiveness began to dip in June. 

Effectiveness of the Moderna and Pfizer COVID-19 vaccines began to drop in June and July as the 'Delta' variant became more prevalent. Moderna had an effectiveness of 76%, while Pfizer's vaccine was 42% effective.

However, the efficacy largely dropped in July as the variant took hold in the United States.

The change in vaccine effectiveness corresponds with a massive surge in the prevalence of the Delta variant in Minnesota, growing from 0.7 percent prevalence in May to more than 70 percent in July.

Meanwhile, the Kent 'Alpha' variant, the previous dominant strain in the U.S., decreased in prevalence from 85 percent to 13 percent over the same time period. 

Even despite a rise in breakthrough infections, the vaccines were still effective in preventing hospitalizations and severe cases from the virus, with both having a hospitalization rate of under 25 percent.   

Research was complied by monitoring samples of people who contracted COVID's Delta variant - and what shot they had - in Minnesota from January to July.   

While breakthrough cases became more common in July, the rate of hospitalization remained low, with both being more than 75 percent effective

The rise of Delta variant prevalence in Minnesota, from 0.7% prevalence in May to more than 70% in July, correlates with the drop in effectiveness of the vaccines

Unvaccinated people also still made up a vast majority of cases.

Still, vaccinated people being able to contract the virus is a worrying prospect for health officials.

Data from the Centers for Disease Control and Prevention finds that vaccinated people who contract the Delta variant release similar viral loads to unvaccinated people, meaning they may be just as able to spread the virus.

While the risk is minimal, some vaccinated people still may be hospitalized, suffer long term negative effects, or even die, from COVID-19.

The Delta variant being able to bypass the existing vaccines also confirms what many feared, that the virus could potentially mutate to a point where it can bypass vaccines.   

Last month, Pfizer published data showing its vaccine's efficacy drops to 86 percent after six months.

Fauci was also keep to dispute suggestions that this means Americans wanting to have a third 'booster shot' of a COVID vaccine should seek out Moderna's injection.

The highly contagious Delta variant is the dominant strain in the U.S., and there are fears that it has a unique ability to cause breakthrough cases among those who are fully vaccinated.

That said, there is also growing conversation about booster shots being made available for Americans in the near future to continue immunity against virus variants.

Last week, the Food and Drug Administration gave emergency approval to a third booster shot of COVID for people who are immunocompromised or have certain underlying conditions.   

However, despite boosters being approved, Fauci warned that same week that he feared a vaccine-resistant variant could form in the near future if the virus continued to spread.   

It is a change of tone from other health officials in recent weeks, including National Institute of Health Director Dr Francis Collins, who said last week booster shots were not necessary. 

Currently, there are three available Covid vaccines in the United States.

The Pfizer vaccine is the most popular, having been used 197 million times since it received FDA emergency use authorization in December 2020.

The Moderna vaccine, which was also given EUA in December, has been used more than 140 million times.

Only one single dose vaccine is available in the U.S. -  the Johnson & Johnson vaccine - which has been used 13.7 million times.