Pfizer’s RSV Vaccine for Older Adults Linked to Guillain-Barré Syndrome, But Drugmaker Says It’s ‘Safe’

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People who receive Pfizer’s respiratory syncytial virus (RSV) vaccine should be monitored for Guillain-Barré syndrome, according to the authors of a Pfizer-funded study published this week in the New England Journal of Medicine (NEJM).

The paper — one of several published Wednesday reporting interim analyses for Pfizer’s phase 3 clinical trials for the RSV vaccine — concluded the vaccine was effective in preventing RSV in adults age 60 and over “without evident safety concerns.”

But that same article also flagged Guillain-Barré syndrome as a safety concern moving forward with the vaccine.

“If RSVpreF vaccine [Pfizer’s RSV vaccine] is approved and recommended, these adverse events warrant close monitoring in future studies and with real-world data and post-marketing surveillance,” the authors of the NEJM study said.

The U.S. Food and Drug Administration (FDA) is expected to approve Pfizer’s RSV vaccine for older adults in May.

Safe and effective?

Guillain-Barré syndrome is a rare disorder in which the body’s immune system attacks its own nerves. Symptoms can range from brief weakness to paralysis.

The FDA asked Pfizer to include the condition as an “important potential risk” of the vaccine and to develop a safety study to monitor for potential cases if the shot is approved, CNBC reported.

When the FDA vaccine advisory panel met in February to review Pfizer’s data pre-publication, there was substantial disagreement about the data on safety and effectiveness, although the majority of the committee voted to recommend the vaccine for approval.

Four of 12 committee members voted that the safety data was not adequate for approval — and one abstained — because of their concerns with the Guillain-Barré cases.

Four committee members also voted the evidence of vaccine effectiveness was not adequate for approval, while seven said it was and one member abstained.

In the NEJM study, one person developed Guillain-Barré syndrome and another developed Miller Fisher syndrome, a subset of Guillain-Barré. The symptoms appeared six and seven days post-vaccination, respectively.

The person with Miller Fisher syndrome recovered. The person diagnosed with Guillain-Barré continues to suffer from loss of motor function.

CNBC reported:

“In the New England Journal of Medicine article, the scientists said the two cases occurred in patients who were in an age group that has an increased risk of developing Guillain-Barré. Potential factors other than the vaccine also could have caused the individuals to develop the syndrome, they added.

“But the FDA said the agency views the Guillain-Barré cases as possibly related to the vaccine because the patients developed the syndrome shortly after receiving the shot, according to briefing documents published in February.

“Pfizer concluded that the cases were unrelated, and the clinical trial’s data monitoring committee did not identify any safety concerns with the vaccine.”

Dr. Hana El Sahly, the FDA committee chair and professor of molecular virology and microbiology and infectious diseases at the Baylor College of Medicine, said Guillain-Barré has an incidence of about 1 in 100,000 among people ages 60 and older. But in the vaccine trial, the rate was closer to 1 in 9,000, which is significantly higher.

“It’s significant in terms of incidence,” she said. The FDA advisors told Pfizer that safety monitoring for Guillain-Barré after FDA approval “would be crucial,” CNBC reported.

There is currently no vaccine approved to prevent RSV, a lower respiratory disease that is one of the most common causes of childhood cold-like illness and was first discovered in humans in 1956.

The illness is mild for most people.

In children under age 5, RSV causes 58,000 to 80,000 hospitalizations per year and 100 to 300 deaths.

In adults ages 65 and older, RSV causes 6,000 to 10,000 deaths and 60,000 to 160,000 hospitalizations per year, according to the Centers for Disease Control and Prevention…