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. 2026 Mar 4:77:128345.
doi: 10.1016/j.vaccine.2026.128345. Online ahead of print.

A Phase IIa randomized clinical trial of a respiratory syncytial virus and human metapneumovirus combination protein-based virus-like particle vaccine in adults 60-85 years of age

Matthew Davis  1 , Craig Shapiro  2 , Max Ciarlet  3 , Elizabeth M Adams  3 , Nicholas Hourguettes  3 , April E Engram  3 , Judy Wen  3 , Himanshu Bansal  4 , Kathryn Shoemaker  4 , Wasima Rida  3 , Anastasia A Aksyuk  5 , Jennifer Price  3 , Tope Oyedele  6 , Lee-Jah Chang  7 , Niranjan Kanesa-Thasan  3
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Free article

A Phase IIa randomized clinical trial of a respiratory syncytial virus and human metapneumovirus combination protein-based virus-like particle vaccine in adults 60-85 years of age

Matthew Davis et al. Vaccine. .
Free article

Abstract

Background: Respiratory syncytial virus (RSV)- and human metapneumovirus (hMPV)-associated lower respiratory tract disease (LRTD) contributes substantially to morbidity and mortality in older adults. IVX-A12 is an investigational combination vaccine comprised of two virus-like particles computationally designed to elicit immune responses against RSV and hMPV. In a Phase I randomized trial, IVX-A12 was well tolerated and elicited RSV- and hMPV-specific neutralizing antibody (nAb) responses in adults 60-75 years of age.

Methods: In this Phase IIa trial, healthy adults 60-85 years of age, including participants with stable, chronic conditions, were randomized 2:2:1 to receive one intramuscular dose of IVX-A12 (150 μg RSV/150 μg hMPV) with/without MF59® (oil-in-water adjuvant), or placebo (diluent), stratified by age group (60-69/70-85 years). Safety and immunogenicity were assessed through 365 days post-vaccination.

Results: Overall, 264 participants received IVX-A12 (n = 211) or placebo (n = 53). Solicited adverse reactions were mild-to-moderate in severity and were reported by 57.3% (n = 59/103), 75.0% (n = 81/108), and 37.7% (n = 20/53) of recipients of unadjuvanted IVX-A12, IVX-A12 + MF59®, and placebo, respectively. IVX-A12 induced increases in nAbs against RSV and hMPV. From baseline to Day 28, in IVX-A12 (±MF59®) recipients, nAbs against RSV A and B increased 5-6- and 3-4-fold, respectively, and nAbs against hMPV A and B both increased 2-3-fold. In IVX-A12 recipients, all except hMPV A nAbs remained above baseline levels at Day 365 and were higher than in placebo recipients. Addition of MF59® to IVX-A12 did not boost antibody responses nor increase their duration. Safety and immunogenicity were similar between the stratified age groups.

Conclusions: IVX-A12 was well tolerated and induced RSV- and hMPV-specific antibody responses in adults 60-85 years of age. This trial demonstrated the feasibility of an RSV/hMPV combination vaccine.

Keywords: Human metapneumovirus; IVX-A12; Respiratory syncytial virus; Vaccine; Virus-like particle.

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Conflict of interest statement

Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: April E Engram, Elizabeth M Adams, Jennifer Price, Judy Wen, Max Ciarlet, Nicholas Hourguettes, Niranjan Kanesa-thasan, and Wasima Rida are current or former employees of Icosavax, a member of the AstraZeneca group, and may or may not hold AstraZeneca stock or stock options. Max Ciarlet and Niranjan Kanesa-thasan hold patents for a “virus-like particle vaccine for respiratory syncytial virus” and a “multivalent vaccine for paramyxoviruses and uses thereof.” Anastasia A. Aksyuk, Himanshu Bansal, Kathryn Shoemaker, Tope Oyedele, and Lee-Jah Chang are employees of AstraZeneca, and may or may not hold AstraZeneca stock or stock options. Elizabeth M Adams received consulting/advisory fees from Quigley BioPharma LLC. Matthew Davis and Craig Shapiro have no competing interests to declare. All authors attest they meet the ICMJE criteria for authorship.

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