A health worker prepares a flu shot before administering it to a local resident in Los Angeles, the United States, on December 17, 2022.
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people who receive PfizerRSV vaccine for older adults should be monitored for Guillain-Barre syndrome after two people developed the nervous system disorder after receiving the vaccine, 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 disease in adults aged 60 and over with no apparent safety concerns. But they flagged the Guillain Barre cases as a potential cause for concern in the future.
“If the RSVpreF vaccine is approved and recommended, these adverse events warrant close monitoring in future studies and with real world data and post-marketing surveillance,” the scientists wrote. The study, released on Wednesday, was supported by Pfizer.
Guillain-Barré Syndrome is a rare condition 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 from severe cases.
The scientists’ call for close monitoring for a possible link between the vaccine and Guillain-Barre is in line with the Food and Drug Administration’s position.
The agency has asked Pfizer to include Guillain-Barre as an “important potential risk” of the vaccine and to develop 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 advisors approved the vaccine in February, although there was significant disagreement at that meeting. Seven consultants said the safety data was sufficient for 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 at increased risk of developing Guillain-Barre. Possible factors other than the vaccine could also have led to the individuals developing the syndrome, they added.
But the FDA said the agency is considering the Guillain-Barre cases as possibly vaccine-related because patients developed the syndrome shortly after receiving the vaccine, according to briefing documents released in February. Pfizer concluded that the cases were unrelated and the clinical trial data monitoring committee found no safety concerns with the vaccine.
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Pfizer’s vaccine is in the running to become the first RSV vaccine ever approved for older adults. According to the Centers for Disease Control and Prevention, RSV kills between 6,000 and 10,000 seniors each year. It also causes 60,000 to 160,000 hospital admissions in the age group annually.
According to results published in the New England Journal of Medicine, the vaccine was 86% effective in preventing lower respiratory disease with three or more symptoms and 66% effective in preventing disease with two or more symptoms. The injection is given as a single dose of 120 micrograms.
While the syringe promises to reduce hospitalizations and deaths from RSV in seniors, FDA advisers were concerned about the Guillain-Barre cases at their February meeting.
dr Hana El Sahly, the FDA committee chair, said Guillain-Barre has an incidence of about 1 in 100,000 in people age 60 and older. But in the vaccine study, the rate was closer to 1 in 9,000.
“So that’s important if we look at it at that level,” El Sahly said. She acknowledged that there is still uncertainty as to what the true rate of the disease would be among vaccine recipients.
“But nonetheless, it’s significant in terms of incidence,” she said of the two cases. The consultants who endorsed the vaccine also said safety monitoring will be crucial following a possible FDA approval.
A 66-year-old man in the United States was diagnosed with Guillain-Barre, and a woman of the same age in Japan was diagnosed with a variant of the syndrome called Miller Fisher. Patients developed symptoms seven and eight days after vaccination, respectively.
The man had a history of high blood pressure and suffered a heart attack shortly before he was diagnosed with Guillain-Barre and the woman had a history of diabetes. The FDA doesn’t see the heart attack as vaccine-related.
The man’s symptoms disappeared 6 months after onset, and the woman’s symptoms completely disappeared 3 months after onset.