The purpose of this study is to test the safety and tolerability of LY3819253 when it is given by injection just under the skin to healthy participants. Blood tests will be done to check how much LY3819253 is in the bloodstream and how long the body takes to eliminate it. Participation could last up to 16 weeks and may include up to six visits to the study center, with a one-week overnight stay.

Inclusion Criteria:

• Are overtly healthy as determined by medical evaluation including medical history and physical examination
• Are willing to follow study procedures, including having nasal or nasopharyngeal swabs collected
• Have a body mass index (BMI) within the range of greater than or equal to (≥)18.5 to less than (<)35 kilograms per square meter (kg/m²)
• Male participants must agree to adhere to contraception restrictions
• Female participants must be of non-childbearing potential

Exclusion Criteria:

• Have or have had known or suspected severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection

• Have a history or presence of cardiovascular (including hypertension), respiratory, hepatic, renal, gastrointestinal, endocrine, hematological, psychiatric, or neurological disorders that, in the opinion of the investigator, are capable of

  • Significantly altering the absorption, metabolism, or elimination of drugs
  • Constituting a risk while taking the investigational product, or
  • Interfering with the interpretation of data

• Have significant allergies to humanized monoclonal antibodies (mAbs)

• Have any of the following that are clinically significant:

  • Multiple or severe drug allergies, or
  • Intolerance to topical corticosteroids, or
  • Severe posttreatment hypersensitivity reactions (including, but not limited to, erythema multiforme major, linear immunoglobulin A dermatosis, toxic epidermal necrolysis, or exfoliative dermatitis)

• Have had lymphoma, leukemia, or any malignancy within the past 5 years, except for basal cell or squamous epithelial carcinomas of the skin that have been resected with no evidence of metastatic disease for 3 years

• Have had breast cancer within the past 10 years

• Show evidence of human immunodeficiency virus (HIV) infection and/or positive human HIV antibodies

• Show evidence of current hepatitis C (that is, test positive for anti-hepatitis C antibody with confirmed presence of hepatitis C virus [HCV] ribonucleic acid [RNA])

All randomized participants.

Baseline to Follow-up (up to 85 days)

All randomized participants who received at least one dose of study drug.