FDA adds warning to RSV shots from GSK, Pfizer
GSK’s and Pfizer’s vaccines for respiratory syncytial virus must carry labels warning of a possible increased risk of a rare neurological disorder, the Food and Drug Administration said Tuesday.
The FDA has not determined a causal link between the shots and the condition, called Guillain-Barré syndrome, or GBS. The agency also reaffirmed that the benefits of both Pfizer’s Abrysvo and GSK’s Arexvy outweigh their risks.
The new labeling is based on postmarketing monitoring for GBS in older adults who received either Abrysvo or Arexvy, as well as clinical trial data and reports to a safety database maintained by the FDA. Taken together, this data suggested an increased, but low, risk of GBS during the six weeks following immunization, the agency said.
GBS can cause damage to nerve cells, leading to muscle weakness and in some cases partial paralysis. The rare side effect is also associated with use of other vaccines like flu shots, as well as the withdrawn COVID-19 vaccine developed by Johnson & Johnson.
The FDA’s analysis compared rates of GBS cases in vaccinated individuals to estimated background rates of the disorder. It found an estimated 9 excess cases of GBS for every million doses of Abrysvo, and an estimated 7 excess cases per million doses of Arexvy administered to adults 65 years of age and older.
Advisers to the Centers for Disease Control and Prevention have also been monitoring for the side effect, including at a meeting early last year, when they weighed changes to vaccination recommendations, and in October.
“During the October 2024 [CDC] meeting, the FDA presented an update to their self-controlled case series study in adults 65 and older,” a Pfizer spokesperson said to BioPharma Dive in an email. “Although not statistically significant, the data suggest an increased risk of GBS within 42 days following vaccination with Abrysvo.”
In a separate statement to BioPharma Dive, a GSK spokesperson said the company is “committed to monitoring and ensuring the safety of all our products, including Arexvy.”
“GSK has ongoing studies to further evaluate safety, including any potential association with GBS,” the spokesperson added. “We remain confident in the benefit-risk profile of Arexvy for the prevention of [RSV-lower respiratory tract disease.]”
Arexvy was the first RSV vaccine approved for older adults in May 2023, with Pfizer’s Abrysvo following shortly after. A third vaccine, from Moderna, was cleared in 2024. (No GBS cases were reported in Moderna’s clinical trials and postmarketing monitoring data are not yet available.)
Abrysvo is also OK’d for maternal use and was recently approved in some adults aged 18 to 59 years old. Arexvy also recently gained expanded authorization for use in high-risk adults aged 50 to 59 years.
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