evidence: Whereas the Pfizer/BioNTech vaccine includes 30 micrograms of mRNA in each dose, Moderna’s original shot has 100 micrograms (Moderna boosters and omicron-updated bivalent and monovalent doses have 50 micrograms); the two vaccines also use a different mix of lipids. These differences may explain why Moderna’s vaccine appears to produce more expected side effects than its competitor. [...] Some data indicate that the Moderna vaccine is more likely than the Pfizer/BioNTech vaccine to cause rare cases of myocarditis or pericarditis. [...] The link between the Moderna and Pfizer/BioNTech vaccines and rare cases of heart inflammation has been confirmed in subsequent work. A 2024 report from the National Academies of Sciences, Engineering, and Medicine "found convincing evidence that established a causal relationship with myocarditis" for both vaccines. The report, which looked at potential vaccine harms that were the subject of compensation claims, was not able to establish a causal relationship between the two vaccines and any other purported harms — in some cases favoring rejection of a causal relationship and in others finding insufficient data to draw a conclusion.