FDA says Guillain-Barre syndrome a potential risk of Pfizer RSV vaccine

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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.

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Food and Drug Administration looks at potential risk of Guillain-Barré syndrome pfizerThe company has asked to conduct a safety study if an RSV vaccine for older adults and a shot is approved this spring, according to agency briefing documents published Friday.

Of the nearly 20,000 vaccine recipients in the Phase III trial, two people in their 60s who received Pfizer’s shot were diagnosed with Guillain-Barré syndrome, according to an FDA document. There were no cases in the placebo group of the trial, the people who didn’t get the shot.

Guillain-Barre syndrome, or inflammatory neuropathy, is a rare disorder in which the body’s immune system mistakenly attacks the 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 there are other possible explanations for the cases. But it said it would conduct a safety study to further assess Guillain-Barré syndrome following possible approval. The company said it did not identify any safety concerns during the trial and that the vaccine was well tolerated.

I also had a possible case of Guillain-Barré syndrome. GSKK’s RSV vaccine trial, but the company said there was insufficient evidence to confirm the diagnosis. According to the FDA, GSK has listed Guillain-Barre as a significant potential risk in its safety monitoring plan. The agency said it would review the plan and make recommendations as needed.

The FDA published the briefing documents ahead of its advisory committee meetings next week. The advisers will vote Tuesday on whether Pfizer’s efficacy and safety data support FDA approval. They will also vote Wednesday on GSK’s RSV vaccine for older adults.

No approved RSV vaccine exists. The virus causes anywhere from 6,000 to 10,000 deaths among senior citizens, although the death rate varies from season to season.

Pfizer’s vaccine was 85% effective in preventing lower respiratory tract disease and GSK’s shot was 83% effective, according to an FDA review of the companies’ data.

Guillain-Barre Case

In Pfizer’s trial, a 66-year-old man in the US with a history of high blood pressure developed symptoms of Guillain-Barre seven days after vaccination. The man had suffered a heart attack before the symptoms started, was admitted to the hospital and underwent angioplasty. The FDA does not consider heart attacks to be related to the RSV vaccine.

This person developed lower back pain eight days after vaccination and then weakness in his lower limbs on day 14. He was again hospitalized after a fall and was later diagnosed with Guillain-Barré syndrome. His symptoms began to improve after treatment and he was in recovery six months after the start, according to the FDA.

In another case, a 66-year-old woman from Japan with a history of type 2 diabetes developed a severe case of Miller Fisher syndrome, a variant of Guillain-Barre. She experienced fatigue nine days after vaccination, a sore throat the next day, and poor muscle control on the 10th day. She was admitted to the hospital 19 days after vaccination, but her symptoms fully recovered within three months.

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The FDA said it agreed with investigators that the cases were possibly related to Pfizer’s vaccines. But Pfizer pointed to other possible explanations in its briefing document. The company pointed to the man’s heart attack and 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 approximately 3 cases per 100,000 people per year, Pfizer should consider the incidence as a significant potential risk in its safety monitoring.

“Given the tentative association and biological plausibility, FDA agrees with the investigators’ assessment that these events were possibly related to the vaccine study,” the agency said.

In GSK’s case, a 78-year-old woman in Japan developed weakness in the lower limbs nine days after receiving her first dose of the RSV vaccine, according to an FDA briefing document. She was participating in an open-label study that had no placebo arm for comparison.

The woman had difficulty walking the next day and developed upper limb and respiratory muscle weakness over the next three days. She was hospitalized and treated for Guillain-Barré syndrome. The FDA and the study investigators consider the case to be related to the vaccine.

But GSK said in its briefing document that the Guillain-Barré diagnosis had not been confirmed because of the absence of test results and because there was no information about whether alternative causes had been investigated. The company said the patient’s case was resolved after six months.

CDC advisors grapple with risks, benefits

The Committee for Disease Control and Prevention’s independent vaccine advisors grappled with three cases of Guillain-Barre syndrome during a meeting open to the public on Thursday. Dr. Michael Melgar, a CDC official, told the committee that it is difficult to determine whether the cases represent a real safety concern associated with the shots, or if they are random incidents.

“Measures of relative and absolute risk were not calculated because of the small number of events,” Melgar told committee members.

But a workgroup of physicians and health officials that reviewed the available data agreed that if the vaccines are approved by the FDA, safety monitoring will be important, Melgar said.

Melgar said most of the working group felt the potential benefits of the vaccines would outweigh the potential risks for people age 65 and older. A minority thought that the risk-benefit balance was uncertain due to Guillain-Barre cases.

Although Pfizer and GSK have asked the FDA to approve their respective vaccines for people 60 and older, the CDC workgroup has generally supported the recommendation for seniors 65 and older. The CDC advisory committee did not vote on any recommendations for RSV vaccines this week.

Dr. Sarah Long, a member of the working group, said the cases gave her pause because the incidence of Guillain-Barré syndrome increases with age, meaning seniors may be more at risk if a link to the vaccine is found at some point. There may be risk.

Dr. Grace Lee, chair of the CDC advisory committee, said more data is needed because respiratory viral illnesses also cause Guillain-Barre syndrome. It is possible that vaccines may prevent more cases of Guillain-Barre syndrome by protecting against disease caused by RSV.

“Maybe you’re doing more prevention, and we don’t know for sure what the rate is, but I think the balance is going to be really helpful, at least I should be able to understand that the benefit —how to think about risk balance,” said Lee, associate chief medical officer at Stanford Children’s Health. “Then I can understand whether 60-year-olds or 65-year-olds make sense.”

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