The exact rules in the AMA Manual of Style can be found in the link below.
About NEJM. New England Journal of Medicine. Accessed May 21, 2021. https://www.nejm.org/about-nejm/about-nejm
Zika travel information. Centers for Disease Control and Prevention. January 26, 2016. Updated December 10, 2020. Accessed May 11, 2021. https://wwwnc.cdc.gov/travel/page/zika-travel-information
MedWatch: the FDA safety information and adverse event reporting program. Food and Drug Administration. Updated May 11, 2021. Accessed May 11, 2021. https://www.fda.gov/safety/medwatch-fda-safety-information-and-adverse-event-reporting-program
Radcliffe S. FDA authorizes Pfizer-BioNTech COVID-19 vaccine for children ages 12–15. Healthline. May 10, 2021. Accessed May 11, 2021. https://www.healthline.com/health-news/children-as-young-as-12-may-soon-have-access-to-covid-19-vaccine