AstraZeneca, Pfizer COVID-19 vaccines effective against Delta variant, study finds

Both the AstraZeneca and Pfizer-BioNTech COVID-19 vaccines maintained effectiveness against the Delta variant in a recent study, with researchers noting "no evidence of widespread complete escape from neutralization." The study, of which a pre-proof appeared in Cell, said it would "seem likely from these results" that the vaccines would provide protection against the B.1.617 variant, "though an increase in breakthrough infections may occur as a result of the reduced neutralizing capacity of sera."  

The Delta variant, which first originated in India, has been dubbed a variant of concern by both the U.S. Centers for Disease Control and Prevention (CDC) and the World Health Organization as it’s increasingly turning up in surveillance data across the world. 

Officials have been concerned about the increasing rates of transmissibility and the risk of hospitalization among individuals who are infected with the variant, particularly those who have not received a vaccine yet. 

"We are encouraged to see the non-clinical results published from Oxford and these data, alongside the recent early real-world analysis from Public Health England, provide us with a positive indication that our vaccine can have a significant impact against the Delta variant," Mene Pangalos, executive vice president of BioPharmaceuticals R&D, said in a press release following the pre-proof. "This gives us great hope that even as these new variants continue to spread, our vaccine would continue to provide protection for people across the world and help turn the tide of the pandemic for the people of India." 

The University of Oxford-led study also noted that the vaccines’ neutralization of the Delta variant was comparable with that seen against the Alpha and Gamma variants. However, the researchers emphasized the need for two doses as protection following a single shot of the Pfizer-BioNTech vaccine "is limited." 

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They also warned that those who remain unvaccinated but were previously infected by the B.1.351 or P.1. variants "may be more at risk of reinfection" with the Delta variant. 

Officials worldwide have stressed that the Delta variant may pose a risk to the progress made in the fight against coronavirus. In the U.S., where the AstraZeneca vaccine has not yet received approval but the Pfizer-BioNTech jab has, the variant now accounts for about 20% of new cases. On Tuesday, Dr. Anthony Fauci, the nation’s leading infectious disease expert highlighted Pfizer’s demonstrated efficacy against the variant. 

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"Similar to the situation in the U.K., the Delta variant is currently the greatest threat in the U.S. to our attempt to eliminate COVID-19," Fauci said. "Good news, our vaccines are effective against the Delta variant." 

Fox News' Kayla Rivas contributed to this report.