This 1981 photo provided by the Centers for Disease Control and Prevention (CDC) shows an electron micrograph of respiratory syncytial virus, also known as RSV.
CDC via AP
The Food and Drug Administration sees a possible risk of Guillain-Barre syndrome Pfizer‘s RSV vaccine for older adults and has asked the company to conduct a safety study if the vaccine is approved this spring, according to agency briefing papers released on Friday.
According to the FDA document, two people in their 60s who received Pfizer’s vaccine were diagnosed with Guillain-Barre syndrome, out of about 20,000 vaccine recipients in the Phase 3 study. There were no cases in the study’s placebo group, the people who did not receive the injection.
Guillain-Barré Syndrome, or inflammatory neuropathy, is a rare condition in which the body’s immune system mistakenly attacks nerves. Symptoms range from brief weakness to paralysis, according to the National Institutes of Health. Most people recover even from severe cases.
Pfizer said in its briefing document that the cases have other possible explanations. However, it said it would conduct a safety study to further evaluate Guillain-Barré syndrome after a possible approval. The company said it did not identify any safety concerns during the study and that the vaccine was well tolerated.
There was also a possible case of Guillain-Barré Syndrome in GSK‘s RSV vaccine trials, but the company said there was insufficient evidence to confirm a diagnosis. According to the FDA, GSK has listed Guillain-Barre as an important potential risk in its safety monitoring plan. The agency said it will review the plan and make recommendations as needed.
The FDA released the briefing documents ahead of its advisory committee meetings next week. Advisors will vote on Tuesday whether Pfizer’s efficacy and safety data support FDA approval. They will also vote on GSK’s RSV vaccine for older adults on Wednesday.
There is no approved RSV vaccine. The virus causes between 6,000 and 10,000 deaths among seniors annually, although mortality varies from season to season.
According to an FDA review of the companies’ data, Pfizer’s vaccine was 85% effective in preventing lower respiratory tract disease and GSK’s vaccine was 83% effective.
The Guillain Barre Falls
In Pfizer’s study, a 66-year-old man in the US with a history of high blood pressure developed Guillain-Barre symptoms seven days after vaccination. The man had a heart attack before symptoms began, was hospitalized and underwent angioplasty. The FDA does not see the heart attack as related to the RSV vaccine.
Eight days after the vaccination, the man developed back pain and, on the 14th day, weakness in his lower extremities. He was hospitalized again after a fall and was subsequently diagnosed with Guillain-Barre Syndrome. His symptoms began to improve after treatment and disappeared six months after onset, according to the FDA.
In a second case, a 66-year-old woman in Japan with a history of type 2 diabetes developed severe Miller-Fischer syndrome, a variant of Guillain-Barre. She suffered from fatigue nine days after the vaccination, a sore throat the next day and poor muscle control on the tenth day. She was hospitalized 19 days after the vaccination, but her symptoms completely disappeared in three months.
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The FDA said it agrees with investigators that the cases may be related to Pfizer’s vaccines. But Pfizer said in its briefing document that there are other possible explanations. Noting the man’s heart attack, the company said the woman had symptoms of an upper respiratory infection.
But the FDA said that given the incidence of Guillain-Barre syndrome in the general population is about 3 cases per 100,000 people annually, Pfizer should consider the incidents as an important potential risk in its safety surveillance.
“Given the temporal association and biological plausibility, the FDA concurs with the investigators’ assessment that these events may be related to the study vaccine,” the agency said.
In the case of GSK, a 78-year-old woman in Japan developed lower-limb weakness nine days after receiving the first dose of the RSV vaccine, according to an FDA briefing document. She took part in an open-label study without a placebo arm for comparison.
The woman had difficulty walking the following day and developed weakness in her upper limbs and respiratory muscles over the next three days. She was hospitalized and treated for Guillain-Barré Syndrome. The FDA and study investigator believe the case is vaccine-related.
But GSK said in its briefing document that a Guillain-Barre diagnosis was not confirmed due to a lack of test results and because there was no information on whether alternative causes had been investigated. The patient’s case was considered settled after six months, the company said.
CDC consultants discuss risks and benefits
The Centers for Disease Control and Prevention’s committee of independent immunization advisors considered the three cases of Guillain-Barré syndrome during a public meeting Thursday. dr Michael Melgar, a CDC official, told the committee it was difficult to determine whether the cases represent an actual safety issue related to the shooting or whether they were random events.
“Due to the small number of events, measures of relative and absolute risk were not calculated,” Melgar told committee members.
However, a working group of doctors and health officials who reviewed the available data agreed that safety monitoring will be critical if the vaccines are approved by the FDA, Melgar said.
A majority of the working group believed the potential benefits of the vaccines would outweigh any possible risks for people aged 65 and older, Melgar said. A minority considered the balance of benefits and risks uncertain, partly because of the Guillain-Barre cases.
Although Pfizer and GSK have asked the FDA to approve their respective vaccines for people age 60 and older, the CDC working group generally endorsed a recommendation for seniors age 65 and older. The CDC advisory committee did not vote on any recommendations for the RSV vaccines this week.
dr Sarah Long, a member of the working group, said the cases had her concerned because the incidence of Guillain-Barre syndrome increases with age, meaning seniors could be at higher risk if at some point a link with the disease is found vaccine is found.
dr Grace Lee, chair of the CDC advisory committee, said more data is needed because respiratory viral diseases also cause Guillain-Barré syndrome. It is possible that the vaccines could prevent further cases of Guillain-Barre syndrome by protecting against RSV disease.
“They might prevent more and we don’t know exactly what the rate is, but I just think that balance will be really helpful, at least for me, to understand how to think through the risk-benefit balance.” , said Lee, associate chief medical officer at Stanford Children’s Health, “Then I can understand whether 60-year-old or 65-year-old makes sense.”
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