evidence: Early findings posted ahead of rigorous peer review suggested the Pfizer COVID-19 vaccine declined to 42% effectiveness against infection amid sweeping spread of the delta variant, with the Moderna vaccine declining to 76%. [...] While results indicated the Pfizer and Moderna vaccines were highly effective against COVID-19 infection (76%, 86%, respectively) and hospitalization (85%, 91.6%) the effectiveness against infection dropped by July to 42% and 76%, respectively. [...] Study authors suggested several factors behind the differences observed among the Pfizer and Moderna vaccines, including the dosing, meaning "each mRNA-1273 [Moderna] dose provides three times more mRNA copies of the Spike protein than BNT162b2 [Pfizer], which could result in more effective priming of the immune response."