Investigational RSV Vaccine Efficacious in High-Risk Older Adults in Phase 3 Trial

The investigational respiratory syncytial virus (RSV) prefusion F protein-based vaccine is efficacious against RSV-associated lower respiratory tract infection (LRTI) and RSV-associated acute respiratory infection (ARI) in older adults at increased risk for severe disease. These study results were published in Clinical Infectious Diseases.

Researchers evaluated the efficacy and immunogenicity of an RSV vaccine among high-risk older adults in an ongoing, randomized, placebo-controlled, phase 3 trial (ClinicalTrials.gov Identifier: NCT04886596). Patients considered at increased risk for severe RSV disease were aged 60 years and older with coexisting cardiorespiratory or endocrine/metabolic conditions.

The RSV vaccine was an AS01_E-adjuvanted RSV prefusion F protein-based vaccine (RSVPreF3 OA). Patients were randomly assigned 1:1 to receive either the RSV vaccine (n=12,467) or placebo (n=14,499) prior to the start of the RSV season. The primary study objective was to evaluate the efficacy of the RSV vaccine against the first episode of RSV-associated LRTI or RSV-associated ARI during a single RSV reason. Outcomes were compared between patients with vs without coexisting conditions of interest, and immunogenicity was assessed in a post hoc analysis.

Baseline demographics were similar between patients in the vaccine and placebo groups (mean age, ~69.5 years; ~52% women; ~79% White), as were the number of patients in each group with at least 1 coexisting condition associated with increased risk for severe RSV disease (39.6% and 38.9%, respectively).

Analysis of patients at increased risk for RSV disease showed that the incidence of RSV-associated LRTI was higher among placebo recipients (incidence rate [IR], 6.6-8.9 per 1000 person-years) compared with vaccine recipients (IR, 5.3 per 1000 person-years). Results were similar in regard to the incidence of RSV-associated ARI (IR, 15.2-17.8 vs 13.1 per 1000 person-years, respectively).

The efficacy of the RSV vaccine against RSV-associated ARI was 81.0% (95% CI, 58.9-92.3) in patients with at least 1 condition associated with increased risk for severe disease. For patients with cardiorespiratory conditions and those with endocrine or metabolic conditions, vaccine efficacy was 88.1% (95% CI, 60.9-97.7) and 79.4% (95% CI, 49.4-93.0), respectively. For patients with at least 2 of these conditions, vaccine efficacy was 88.0% (95% CI, 60.5-97.7).

Further analysis showed that the efficacy of the RSV vaccine was higher against RSV-associated LRTI. Vaccine efficacy was 94.6% (95% CI, 65.9-99.9) in patients with at least condition of interest, with efficacy rates of 92.1% (95% CI, 46.7-99.8) and 100% (95% CI, 74.0-100) observed in those with cardiorespiratory or endocrine/metabolic conditions, respectively. For patients with at least 2 of these conditions, vaccine efficacy was 92% (95% CI, 46.1-99.8).

In regard to immunogenicity, increases in RSV-A- and RSV-B-neutralizing geometric mean titers between baseline and 31 days after vaccination were higher among patients with (11.0-fold and 9.1-fold increase, respectively) vs without (9.8-fold and 8.3-fold increase, respectively) at least 1 condition of interest.

This study may have been limited as the efficacy and immunogenicity analyses were descriptive and not adjusted for multiplicity.

“Given that people with these chronic illnesses bear the brunt of the RSV disease burden in older adults, this vaccine could have a positive impact on public health,” the researchers concluded.

Disclosure: This research was supported by GlaxoSmithKline Biologicals SA; and multiple study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.

This article originally appeared on Infectious Disease Advisor