The Moderna COVID-19 vaccine may be more effective than the Pfizer/BioNTech vaccine against the Delta variant of coronavirus, suggest two studies posted on medRxiv, yet to be peer-reviewed. 

A study with over 50,000 patients in the Mayo Clinic Health System noted that the effectiveness of Moderna vaccine declined to 76% in July, as the Delta variant became dominant, down from 86% in early 2021. During that period, the effectiveness of the Pfizer vaccine declined to 42% from 76%. While both the mRNA vaccines are effective at preventing hospitalization related to COVID-19, a booster dose of the Moderna jab may be required soon for those who received Pfizer or Moderna vaccines earlier this year, stated Dr. Venky Soundararajan of Massachusetts data analytics company nference.

In another study, elderly residents of nursing home in Ontario developed stronger immune responses, particularly to concerning variants, following the administration of Moderna vaccine compared to that after the Pfizer/BioNTech vaccine… (Reuters, August 10, 2021)