Moderna 76% effective against Covid-19 Delta variant, Pfizer 42%: Study
India TV NewsVaccines against Covid-19 that were developed by US drug makers Pfizer and Moderna may not be as effective against the 'Delta' variant compared to as they were against the original strain of the virus, suggests a new study. Researchers from the Mayo Clinic in Minnesota, US, found that the Pfizer-BioNTech vaccine was only 42 percent effective against infection in July, while the Moderna vaccine was only 76 percent effective, the Daily Mail reported. "Comparing rates of infection between matched individuals fully vaccinated with mRNA-1273 versus BNT162b2 across Mayo Clinic Health System sites in multiple states, mRNA-1273 conferred a two-fold risk reduction against breakthrough infection compared to BNT162b2," the researchers wrote in the study, not yet peer-reviewed, and published on pre-printer server medRxiv.org. From January to June, the vaccines as claimed remained effective around 90 percent, but began dipping in June and largely dropped in July as the variant took hold in the US. 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, the study showed.