The purpose of this clinical study is to learn about the safety and effects of the study medicine (called PF-07999415) in healthy adult participants.

This study is seeking volunteers aged 18 to 65 years old who do not have any major health issues.

Some participants in this study will receive a single dose of PF-07999415 as a shot in the thigh, abdomen, or arm at the study clinic. Afterward, participants will stay in a hospital-like setting for 2 weeks, where they will be monitored for reactions to the study medicine.

The study team will compare the experiences of people receiving PF-07999415 to those of the people who do not. This will help the study team decide if PF-07999415 is safe.

Participants will take part in this study for 3 to 7 months. During this time, participants will stay at the healthcare facility for 2 weeks and then come back for study visits every 2 weeks until completing the study.

Inclusion Criteria:

• Male and female participants of non-childbearing potential aged 18 to 65 years, inclusive, at screening who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and cardiac monitoring.
• Body Mass Index (BMI) of 18-33 kg/m2 and a total body weight >50 kg (110 lb).

Exclusion Criteria:

• Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, dermatological, gastrointestinal, cardiovascular, hepatic, psychiatric, neurological, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing).
• Any medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality or other conditions that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
• Previous administration of an investigational product (drug or vaccine) within 30 days (or as determined by the local requirement) or 5 half-lives preceding the first dose of study intervention used in this study (whichever is longer). Participation in studies of other investigational products (drug or vaccine) at any time during participation in this study.

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.