First RSV vaccine approved by FDA, a moment that has been six decades in the making

After a six-decade search, scientists have finally developed the first vaccine to protect against respiratory syncytial virus, or RSV, and additional vaccines are in the pipeline.

The US Food and Drug Administration has given the green light to Arexvy, created by pharmaceutical company GSK, which is specifically designed as a single shot for adults aged 60 years and older.

If recommended by the US Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices, Arexvy could be made available to seniors as soon as this autumn. The committee next meets in June.

The importance of the new vaccine is highlighted by the fact that, although RSV is generally considered a disease that affects infants and young children, it can be especially hazardous to seniors. According to estimates, around 159,000 American adults aged 65 and above are hospitalised with RSV each year, with between 10,000 and 13,000 dying as a result.

“This is really a wonderful development,” said Dr. Ruth Karron, a professor of international health at Johns Hopkins Bloomberg School of Public Health, who was not involved in the vaccine’s development.

Arexvy, which is 83% effective at preventing lower respiratory tract disease caused by the virus, and 94% effective at preventing severe RSV disease in seniors, uses a small piece of the virus – the F, or fusion, protein – that protrudes from its surface and helps it infect cells in the upper airways. The protein pieces in the vaccine are made in a lab, using cells specially programmed to produce them.

The vaccine builds on a discovery made a decade ago by researchers at the National Institutes of Health, including some of the same scientists who helped develop the Covid-19 vaccines. The researchers found a way to freeze the F protein in the shape it takes before it fuses with a cell. This meant that the body could develop strong antibodies against it.

The GSK vaccine uses this potent pre-fusion form of the protein, combined with an adjuvant – a substance that boosts immune activity.

Dr. Len Friedland, director of scientific affairs and public health at GSK, stated that the vaccine is 94% effective at preventing lower respiratory tract infections in vulnerable seniors with underlying health conditions such as COPD, heart failure or heart disease.

Although there were some side effects reported by people in the clinical trial, such as pain at the injection site and fatigue, these usually resolved within a day or two. There were a small number of serious adverse events, but they were balanced between the group that received the vaccine and the group that received the placebo.

The FDA has required GSK to continue to monitor for signs of Guillain-Barré syndrome, a nerve disorder that can cause paralysis or weakness that rarely follows viral infections and vaccination. It is also requiring the company to study the risk of a condition called acute disseminated encephalomyelitis, a rare type of inflammation that affects the brain and spinal cord. The FDA says two people in the clinical trials for the vaccine developed the condition after getting that shot along with an influenza vaccine.

It is still unknown how long the vaccine’s protection will last, and the researchers will continue to evaluate vaccine efficacy over time. So far, protection appears to last for around a year.

Three other RSV vaccines for older adults are also in the final stages of testing, with Pfizer’s RSV vaccine for older adults expected to receive FDA approval by the end of May. The agency is also reviewing Pfizer’s maternal vaccine to protect infants and is expected to make a decision by the end of August. Moderna is finishing its Phase 3 trial of an mRNA vaccine for RSV in older adults and expects to submit the results to the FDA for approval within the next few months.