Moderna vaccine may be best against Delta: Studies

The mRNA vaccine from Pfizer and BioNTech may be less effective than Moderna’s against the Delta variant, according to two reports posted on medRxiv on Sunday ahead of peer review.

In a study of more than 50,000 patients in the Mayo Clinic Health System, researchers found the effectiveness of Moderna’s vaccine against infection had dropped to 76% in July — when the Delta variant was predominant - from 86% in early 2021. Over the same period, the effectiveness of the Pfizer/BioNTech vaccine had fallen to 42% from 76%, researchers said. While both vaccines remain effective at preventing hospitalisation, a Moderna booster shot may be necessary soon for anyone who got the Pfizer or Moderna vaccines earlier this year, said Dr. Venky Soundararajan, who led the study.

In a separate study, elderly nursing home residents in Ontario produced stronger immune responses — especially to worrisome variants — after the Moderna shot than after the Pfizer jab. The elderly may need higher vaccine doses, boosters, and other preventative measures, said lead reaseracher Anne-Claude Gingras of the Lunenfeld-Tanenbaum Research Institute.