A new global study led by GlaxoSmithKline has found that a single dose of the RSV vaccine Arexvy (RSVPreF3 OA) offers strong and lasting protection against lower respiratory tract disease caused by respiratory syncytial virus (RSV) in adults aged 60 and older.
The vaccine was shown to be effective across three consecutive RSV seasons, marking a major step forward in protecting older adults from this often-overlooked respiratory threat.
RSV is a common virus that usually causes cold-like symptoms, but in older adults—especially those with chronic health conditions such as heart disease, lung disease, diabetes, or kidney failure—it can lead to serious illness, hospitalization, and even death.
Despite decades of research, effective vaccines for RSV only became available in 2023. Among the three vaccines approved for older adults, Arexvy is now the first to demonstrate protection lasting across multiple RSV seasons.
The findings, published in The Lancet Respiratory Medicine, come from a large, Phase III clinical trial called AReSVi-006, which involved 24,972 adults aged 60 or older from 17 countries across Africa, Asia, Oceania, Europe, and North America.
Participants were randomly assigned to receive either one dose of Arexvy or a placebo before the first RSV season. Some of those in the vaccine group were later re-randomized before the second season to receive either a second dose or another placebo, allowing researchers to compare the effects of one vs. two doses.
To track RSV cases, the research team used nasal and throat swabs tested by qRT-PCR to detect RSV A and B. Participants reported symptoms through regular check-ins, and samples were collected if respiratory illness developed. A separate group provided blood samples to measure antibody levels over time.
The results were promising. Over the course of three RSV seasons, a single dose of Arexvy showed 62.9% overall efficacy in preventing RSV-related lower respiratory illness. Protection was stronger against RSV A (69.8%) than RSV B (58.6%).
Older adults between 70 and 79 years old benefited the most, with vaccine efficacy reaching 70.6% in this age group. Among participants with pre-existing medical conditions or in a pre-frail state, protection ranged from 64.7% to 70.1%. However, for people aged 80 or older and those who were fully frail, the number of RSV cases was too small to draw firm conclusions.
As expected, the vaccine’s effectiveness declined over time—from 82.6% in the first season to 48.0% by the third season.
A second dose, given one year after the first, provided 67.8% protection, suggesting that while immunity wanes, revaccination can help maintain protection—though the second dose didn’t significantly outperform the first in long-term results.
Importantly, the vaccine was well tolerated, with serious side effects occurring in fewer than 1% of participants. Investigators reported five deaths as possibly related to the study—three in the vaccine group and two in the placebo group—but these events were rare and carefully reviewed.
The study also found that although antibody levels declined between seasons, they remained above baseline before the third RSV season, offering insight into the vaccine’s lasting immune effects.
Arexvy is now the first licensed RSV vaccine proven to offer protection for up to three years, making it a valuable tool in safeguarding older adults from RSV-related illness. These findings support its continued use and suggest that revaccination might be needed after two to three years to sustain protection.
With RSV posing a serious threat to the health and independence of older adults, this study confirms that even a single dose of Arexvy can offer substantial benefits. As more research is done, experts hope to develop clear guidelines on how often older adults should receive the vaccine to stay protected long-term.
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The research findings can be found in The Lancet Respiratory Medicine.
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