An Observational Study of Moderna COVID-19 Bivalent Vaccines (Original and Omicron BA.4/BA.5) and 2023 Updated mRNA COVID-19 Vaccines (XBB.1.5)

Inclusion Criteria: * Lives in the continental United States (US). * Speaks, reads, and understands English. * Is willing and able to submit vaccination card photo(s) or vaccination records. * Is willing and able to self-collect capillary blood during the study period via an at-home whole-blood collection device. * Is fully vaccinated against COVID-19 per protocol specified criteria. Exclusion Criteria: * Has been diagnosed with significant cognitive impairment or dementia. * Is pregnant or planning to become pregnant during the study period. * Primary mailing address is a Post Office box, Army Post Office, Fleet Post Office, or Diplomatic Post Office address. * Currently lives in a US military base located overseas, or US territories (Puerto Rico, US Virgin Islands, Guam, Northern Mariana Island, or American Samoa). * Is currently participating in a COVID-19 vaccine clinical trial. * Is currently receiving chemotherapy or has received chemotherapy in the past 6 months. * Is currently taking steroids, such as prednisone, for any condition. * Has been diagnosed with and taking immunosuppressants for rheumatoid arthritis, lupus or multiple sclerosis. * Has received an organ transplant. * Is currently undergoing dialysis of any kind (for example, hemodialysis or chronic ambulatory dialysis) for kidney disease.