evidence: Researchers from the Mayo Clinic in Minnesota, US, found that the Pfizer-BioNTech vaccine was only 42 per cent 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 (Moderna Covid vaccine) versus BNT162b2 (Pfizer Covid vaccine) across Mayo Clinic Health System sites in multiple states (Minnesota, Wisconsin, Arizona, Florida, and Iowa). 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a two-fold risk reduction against breakthrough infection compared to BNT162b2," the researchers wrote in the study, not yet peer reviewed, and published on pre-printer server medRxiv.org. [...] Last month, Pfizer published data which showed that its vaccine's efficacy drops to 86 percent after six months.