Safety and Immunogenicity of IVX-A12 in Healthy Older Adults

The main purpose of this study is to evaluate the safety and immunogenicity of three dosage levels (low, medium, high) of the bivalent combination respiratory syncytial virus (RSV)/human metapneumovirus (hMPV) virus-like particle (VLP) candidate vaccine (IVX-A12), compared to placebo, when administered as a single-dose regimen in healthy older adults 60 to 75 years of age.

Inclusion Criteria:Healthy male or non-pregnant female older adults 60 to 75 years of age at the time of first vaccinationParticipants with stable well-controlled chronic conditions such as hypertension without clinical exacerbation of their underlying disease within the previous 12 monthsParticipants able to voluntarily give written informed consent and to comply with study procedures including follow-up to approximately 12 months after first dosingBody mass index (BMI) 17 to 35 kilogram per square meter (kg/m^2), inclusive, at screeningScreening laboratory values must be within the laboratory reference ranges or deemed not clinically significant if within Grade 1 severity on the toxicity scaleExclusion Criteria:Prior receipt of any investigational RSV or hMPV vaccinePrior receipt of another investigational medicinal product (study drug, biologic, or device) not authorized for use in the United States and European Union within the past yearLaboratory-confirmed severe RSV or hMPV infection within the past year prior to enrollmentCurrently enrolled or plan to participate in another clinical study with an investigational agent (including licensed or unlicensed vaccine, drug, biologic, device, blood product, or medication) to be received during the study periodPresence of high-risk comorbidities for severe RSV or hMPV disease (example, significant cardiopulmonary disease)Older adults meeting frail elderly criteria (older persons with medical, nutritional, cognitive, emotional, or activity impairments, as defined by the study site)Acute or chronic progressive, unstable or uncontrolled clinical conditionsAcute illness, with or without fever at the time of planned vaccinationHistory of hypersensitivity or serious adverse reactions to vaccines, such as anaphylaxis, Guillain-Barré, and angioedema, or any known allergies to any component of the IVX-121 and/or IVX-241 vaccine, or hypersensitivity to latexAbnormal function of the immune system resulting from clinical conditions including human immunodeficiency virus, chronic administration of systemic corticosteroids (oral/intravenous/IM at a dose equivalent of greater than (>) 20 milligrams (mg) prednisone in a period of more than 14 days), or administration of immunosuppressive chemotherapy, biologics, or radiotherapy within the past 3 months before study randomizationRefusal to maintain contraceptive practices during the study, and (for women of childbearing potential) to be screened for pregnancy at specified times during the studyReceipt of licensed inactivated vaccines including influenza vaccine within 14 days prior to study vaccine administration on Study Day 0, or with live virus vaccines within 30 days of Day 0Receipt of licensed vaccines is permitted after completion of the study Day 28 visit.Receipt of licensed COVID-19 vaccines is permitted if dosing regimen completed within 21 days prior to study vaccine administration on Day 0 or after completion of the Day 28 visit.