In October 2022, GlaxoSmithKline (GSK) pharmaceutical issued a press release that reported their RSV vaccine reduced severe RSV illness by 94.1 percent in persons 60 years and older. GSK also reported that the vaccine had an overall efficacy of 82.6 percent in their Phase 3 clinical trial. This vaccine combines a recombinant subunit prefusion RSV F glycoprotein antigen (RSVPreF3) with GSK’s proprietary AS01E adjuvant. This adjuvant is a liposome-based adjuvant that contains two ingredients, 3-O-desacyl-4′-monophosphoryl lipid A (MPL) and saponin QS-21, which stimulates the immune system. This adjuvant is also used in the Shingrix herpes zoster (shingles) vaccine, a vaccine that has been associated with an increased risk of Guillain-Barré syndrome (GBS).
While GSK reported their vaccine to be highly efficacious in reducing severe RSV illness in persons 60 years and older, the clinical trials were not sufficiently powered to estimate its efficacy against hospitalization and/or death. In the clinical trials, there were less than five cases of RSV infection and no associated deaths. Additionally, the clinical trial took place during a shift in the seasonal patterns of RSV infections attributed to the COVID-19 pandemic.
The initial clinical trials for GSK’s RSV vaccine were intended for pregnant women, however, trials were permanently halted due to an undisclosed safety signal with the vaccine product.
During the FDA’s Vaccines and Biologics Products Advisory Committee convened on March 1, 2023 to review GSK’s application for licensure, it was reported that one case of Guillain Barre Syndrome (GBS), a rare neurological disorder that causes inflammation of the peripheral nerves with complications that can include temporary or chronic paralysis, including full body paralysis, and may lead to death, had occurred among the 15,400 clinical trial participants. Additionally, there was a higher rate of vaccine recipients who experienced atrial fibrillation, a serious heart disorder that may lead to complications such as stroke, heart attack, or heart failure, in comparison to those who received the placebo.
GSK also reported that in one clinical trial, Study 007, which studied the use of the experimental RSV shot when given at the same time as the quadrivalent influenza vaccine, of the 442 participants, two cases of Acute Disseminating Encephalomyelitis (ADEM) had occurred, with one case resulting in death.
Despite the safety risks, most committee members voted to recommend the product for licensure. Those who voted against the vaccine expressed concerns regarding the case of GBS, as well as the ADEM safety signal when administered along with the flu vaccine. All committee members, however, voted to recommend the experimental RSV shot based on the vaccine’s effectiveness at preventing RSV acute respiratory illness and lower respiratory tract infection.
On May 3, 2023, the FDA licensed use of GSK’s AREXVY RSV vaccine for use in adults 60 years of age and older. The CDC’s Advisory Committee on Immunization Practices (ACIP) voted on June 21, 2023 to recommend use of the vaccine in all persons 60 years and older, based on “shared clinical decision-making”. This recommendation means that eligible individuals may choose to receive the vaccine if they believe that the benefits of vaccination outweigh the risks. In June 2024, the CDC’s ACIP committee revised their RSV vaccine guidance and recommended that adults 60 through 74 years considered at high-risk for severe RSV illness and all adults 75 years and older receive a single dose of RSV vaccine.
The FDA approved the use of GSK’s AREXVY RSV vaccine in persons 50 through 59 years who are at an increased risk for lower respiratory tract infection cause by RSV in June 2024. While this vaccine is FDA approved for use in this population, the CDC does not recommend its use in persons 50 through 59.
