- People who receive Pfizer’s RSV vaccine for older adults should be monitored for Guillain-Barré syndrome, the scientists said in an article published in the New England Journal of Medicine.
- Two people who received the shot during the vaccine trial developed nervous system disorders.
- Scientists say there are other possible explanations for the cases, but the FDA sees them as vaccine-related.
- Pfizer has agreed to conduct a post-approval safety study
- Overall, the scientists concluded that the vaccine was effective without any apparent safety concerns.
A health worker prepares a flu vaccine shot before administering it to a local resident in Los Angeles, U.S., on Dec. 17, 2022.
Xinhua News Agency Getty Images
who accept Pfizer’s RSV vaccine for older adults should be monitored for Guillain-Barre syndrome, after two people developed a nervous system disorder after they received the shot, scientists said in clinical trial results published in the New England Journal of Medicine.
The scientists concluded that the vaccine was effective in preventing lower respiratory tract infections in adults age 60 and older with no apparent safety concerns. But they identified Guillain-Barre cases as a possible cause for concern.
“If the RSVpreF vaccine is approved and recommended, these adverse events warrant close monitoring in future studies and with real-world data and postmarketing surveillance,” the scientists wrote. The study, published Wednesday, was supported by Pfizer.
Guillain-Barré syndrome is a rare disorder in which the body’s immune system mistakenly attacks nerves. Symptoms can range from brief weakness to paralysis, According to the National Institutes of Health. Most people recover, even in severe cases.
Scientists’ calls for closer scrutiny of possible links between vaccines and Guillain-Barre echo the Food and Drug Administration’s position.
The agency asked Pfizer to include Guillain-Barré as a “significant potential risk” of the vaccine and to create a safety study to monitor potential cases if the shot is approved in May. Pfizer has agreed to conduct a safety study
The FDA’s independent advisers endorsed the vaccine in February, although there was considerable dissent at that meeting. Seven advisers said the safety information was sufficient to warrant approval, while four said it was not and one abstained.
In the New England Journal of Medicine article, the scientists said the two cases occurred in patients who were in an age group with an increased risk of developing Guillain-Barre. Potential factors other than vaccines may also cause individuals to develop the syndrome, they added.
But the FDA said the agency considers the Guillain-Barre cases likely related to the vaccine because the patients developed the syndrome shortly after receiving the shot, according to briefing documents released in February. Pfizer concluded that the cases were not related, and the Clinical Trials Data Monitoring Committee did not identify any safety concerns with the vaccine.
Pfizer’s shot is in the running to become the first RSV vaccine approved for older adults. According to the Centers for Disease Control and Prevention, RSV kills 6,000 to 10,000 adults each year. It accounts for 60,000 to 160,000 hospitalizations in the age group annually.
According to results published in the New England Journal of Medicine, the vaccine is 86% effective in preventing lower respiratory tract illness with three or more symptoms and 66% effective in preventing illness with two or more symptoms. The shot is administered as a single, 120-microgram dose.
While the shot promises to reduce hospitalizations and deaths from RSV among seniors, FDA advisers were concerned about the Guillain-Barre case during their meeting in February.
FDA committee chair Dr. Hanna El Sahli said Guillain-Barre has an incidence of 1 in 100,000 in people age 60 and older. But in vaccine trials the rate was as low as 1 in 9,000.
“So it’s important if we take it to this level,” El Sahli said. He acknowledged that there is still uncertainty about what the actual rate of disease will be among vaccine recipients.
“However, it is significant in terms of events,” he said of the two cases. Advisers supporting the vaccine also said safety monitoring would be crucial after any potential FDA approval.
A 66-year-old man in the United States developed Guillain-Barre, and a woman of the same age in Japan was diagnosed with a variant of Miller Fisher syndrome. Patients develop symptoms seven to eight days after vaccination.
The man had a history of high blood pressure and had a heart attack shortly before being diagnosed with Guillain-Barré disease, and the woman had a history of diabetes. The FDA does not view heart attacks as vaccine-related.
Male symptoms resolved six months after onset and female symptoms resolved completely after 3 months of onset.
