The Food and Drug Administration has approved giving GSK's vaccine for respiratory syncytial virus down to age 50 years old, to those who are at higher risk of severe RSV, the company said Friday, making it the first shot greenlit for use in this age group to guard against RSV.

Global vaccine and drugmaker GSK asked the FDA in February to expand approval beyond adults 60 and older, citing data showing the immune response in adults vaccinated from this younger age group looked similar. Further trials are planned looking at adults between 18 and 49 years old, GSK said, with results expected in the second half of this year. 

Two other companies – Pfizer and Moderna – also manufacture RSV vaccines approved for adults 60 and older, and are testing their shots in younger adults. Pfizer told investors last month it was getting ready to submit "positive" data from studies of its own shot down to age 18.

GSK's vaccine will next need to be recommended for adults between 50 and 59 years old by the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices. Their backing, at upcoming meetings in June or October, would tee up insurance coverage.

Vaccinating adults in their 50s for RSV likely has a public health benefit, a work group within the CDC's committee concluded last year ahead of the approval, though it is narrower than for older adults who are at higher risk from their age alone.

Under 60 years old, pre-existing medical issues play larger roles in the risk of RSV infections taking a dangerous turn. 

"A lot of disease comes because the virus is triggering your underlying medical conditions, whether it's COPD, heart failure, etc. So the virus is more of a trigger for exacerbation," said Dr. Phil Dormitzer, senior vice president and global head of vaccines research and development at GSK. 

Dormitzer said GSK had seen "relatively comparable" safety results from its vaccine in this group, compared to when it was given to those 60 and over. Some of the vaccine's side effects did look to be a little stronger, likely as a result of better immune responses in this age group.

The CDC panel has also previously wrestled with rare but serious cases of a neurological disorder called Guillain-Barré syndrome seen after the use of the RSV shots. 

Around 1.5 cases of the syndrome per million doses given of GSK's vaccine have been reported, the CDC said last week. The agency's survey data has found that close to a quarter of adults ages 60 and older had received an RSV shot since they were approved last year.

GSK's trials did not turn up any "concerning" trends of GBS cases in the 50 to 59 age group, Dormitzer said.

"The risk of GBS tends to go up, it's another one of those risks that tends to go up, with age. But there's nothing to indicate that there's any particular risk of GBS," he said.

The CDC panel is also expected to weigh the possibility of whether and when adults will need to start getting booster shots for RSV.
Dormitzer said GSK is planning on presenting more trial results to the CDC committee in June, looking at boosters spaced out as much as three years after an initial shot.

"This is a really key question. People originally anticipated it might have to be an every year immunization. But then we found the duration of protection actually lasts for more than one season, clearly," he said.

In:
• RSV
• Vaccine

Alexander Tin

Alexander Tin is a digital reporter for CBS News based in the Washington, D.C. bureau. He covers the Biden administration's public health agencies, including the federal response to infectious disease outbreaks like COVID-19.

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