RSV vaccine remains effective against distinct viral variants

GSK’s Arexvy vaccine for respiratory syncytial virus (RSV) — the first to be approved for older adults — can remain effective against a range of variants and produces strong antibody responses against distinct viral strains, according to a new study. The study results, published in the journal Science Translational Medicine, indicate that the vaccine could offer enduring protection against both contemporary RSV and future variants, especially when combined with vaccine adjuvants.

RSV is a common, contagious virus that can lead to potentially serious respiratory illness, including lower respiratory tract disease (LRTD). Older adults, including those with underlying medical conditions such as diabetes and chronic heart and lung disease, are at increased risk of severe RSV illness and drive the majority of RSV hospitalisations. This led GSK to develop Arexvy, a vaccine containing the RSV prefusion F protein (RSVPreF3) and a proprietary AS01 adjuvant.

Arexvy was approved by the US FDA in May, following the pivotal AReSVi-006 (Adult Respiratory Syncytial Virus) phase 3 trial in which the vaccine showed statistically significant and clinically meaningful overall efficacy of 82.6% against RSV-LRTD in adults aged 60 years and older, meeting the primary endpoint. But as the COVID-19 pandemic has shown, vaccines can sometimes lose their potency against viral infections as the virus mutates. Therefore, although RSV doesn’t seem to evolve as quickly as SARS-CoV-2 or influenza, research is still needed to determine whether vaccines for the virus will remain effective as the virus’s antigenic sites shift over time.

In the new study, GSK’s Lionel Sacconnay and colleagues used a large dataset of RSV sequences, gathered from 1990 to 2022, to first characterise the most noticeable changes in the virus’s major antigenic sites over time. They selected a panel of six RSV strains with different combinations of these major variations, but found that antibodies induced by RSVPreF3 neutralised all the variants in culture.

The vaccine elicited broad antibody responses in mice and in cows that effectively neutralised the six selected strains, especially when combined with the vaccine adjuvant AS01. A study of serum samples from vaccinated older adults also showed that the adjuvanted RSVPreF3-AS01 vaccine produced a strong antibody response against the RSV strains, suggesting that the adjuvant could help maintain the vaccine’s efficacy.

“We expect RSVPreF3-AS01 to protect older adults against lower respiratory tract diseases not only caused by any contemporary RSV strain, but also by those that may emerge in the future,” the study authors said.

Arexvy will be made available for older adults in the US before the 2023–24 RSV season, which typically starts ahead of the winter months. It is hoped that the product, along with RSV vaccines from other manufacturers, will make it to Australia within the next 2–3 years.

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