Name Info Provider Link
Flu Shot free resource MedlinePlus Health Information https://medlineplus.gov/flushot.html
subscription/membership/fee required Ovid Technologies, Inc. http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=21681390.ui
subscription/membership/fee required Springer https://dx.doi.org/10.1007/s00277-011-1278-0