#Frequency site:bmj.com | site:thelancet.com | site:jamanetwork.com | site:nature.com | site:nejm.org | site:aap.org | site:acc.org | site:cancer.gov | site:www.cdc.gov | site:fda.gov | site:hhs.gov | site:statnews.com | site:orpha.net | site:rarediseases.org | site:beckershospitalreview.com