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FDA committee votes on Pfizer shot for older adults

Blood sample for respiratory syncytial virus (RSV) test

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The Food and Drug Administration’s independent advisors on Tuesday recommended Pfizer’s RSV vaccine for adults ages 60 and older, despite safety concerns after two people who received the shot developed a rare neurological disorder. 

Though a majority of the FDA committee members backed the vaccine, they wrestled with two separate votes on whether the safety and efficacy data are adequate to support the agency’s approval. 

In the first vote, seven members of the committee said the safety data was adequate for an approval, while four said it was not, and one member abstained.

In the second vote, seven members said the effectiveness data was adequate, while four said it was not, and one member abstained.

The vote followed concerns at the FDA and among advisory committee members about two cases of Guillain-Barre syndrome among about 20,000 vaccine recipients. Guillain-Barre is a rare neurological disorder in which the body’s immune system mistakenly attacks the nerves.

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Symptoms can range from brief weakness to paralysis. Most patients, even those with severe cases, recover.

The FDA considers the cases to be possibly linked to the vaccine, said Dr. Nadine Peart Akindele, an agency official. The FDA has asked Pfizer to conduct a safety study on Guillain-Barre syndrome, which the company has agreed to do.

Vaccine effectiveness

Although respiratory syncytial virus causes mild illness in most people, seniors are at higher risk of severe disease. There currently is no approved RSV vaccine for the elderly.

Pfizer’s vaccine contains both strains of RSV, which circulate at the same time during fall and winter. The shot is administered as a single 120 microgram dose.

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The shot was about 86% protective against lower respiratory tract illness with three or more symptoms, and 66.7% effective against the same condition with two or more symptoms, according to an FDA review of Pfizer’s data. The symptoms included wheezing, shortness of breath, rapid and shallow breathing as well as mucus production.

At the time of Tuesday’s meeting, there was not enough data to evaluate the effectiveness of Pfizer’s vaccine against severe disease requiring hospitalization, oxygen support or a mechanical ventilator, according to the FDA. Data was also not available on how long protection from the vaccine will last, according to the agency.

Pfizer also did not have data on how effective the vaccine is for elderly individuals with weak immune systems or for those in frail health, according to the FDA.

Guillain-Barre cases

A 66-year-old man in the U.S. developed Guillain-Barre, and a woman of the same age in Japan was diagnosed with Miller Fisher syndrome, a variant of Guillain-Barre. They developed symptoms seven and eight days after vaccination, respectively. The woman has since recovered, and the man’s symptoms were resolving as of the last update, according to FDA.

Though the FDA views Guillain-Barre syndrome as an important potential risk, Pfizer executive Alejandra Gurtman maintained that the company did not identify any safety concerns during the trial and that the vaccine was well tolerated.

Gurtman pointed to other potential causes of the Guillain-Barre cases, noting that the man had suffered a heart attack and the woman had an upper respiratory tract infection. But Dr. Marie Griffin, an FDA advisory committee member, said the cases raise serious safety concerns.

“It seems to me that one case is a red flag. Two cases is very concerning and it’s concerning to me that Pfizer doesn’t think that there are any safety concerns,” said Griffin, a professor of health policy at Vanderbilt University Medical Center.

Dr. David Kaslow, a senior official in the FDA’s vaccine division, said safety monitoring will be “critically important” if Pfizer’s RSV vaccine is approved.

The FDA is currently reviewing Pfizer’s proposal to study the risk of Guillain-Barre syndrome among Medicare beneficiaries. The FDA has the authority to require such a study after approval if the agency determines that is necessary.

A 61-year-old woman also had an allergic reaction eight hours after vaccination. She had shortness of breath and chest pain, lost consciousness and was hospitalized. Her symptoms resolved five days later. The FDA also considers this case possibly related to the vaccine.

Disease burden

In adults ages 65 and older, RSV causes 6,000 to 10,000 deaths and 60,000 to 160,000 hospitalizations per year, according the Centers for Disease Control prevention. The risk of hospitalization increases with age, and adults ages 70 and older are more vulnerable.

Among adults of all ages hospitalized with RSV, 19% require intensive care and 4% die, according to CDC data from three seasons. Mortality is the highest among seniors.

Pfizer estimates that if 50% of people ages 60 and older receive the shot, the vaccine could prevent more than 5,000 deaths, 68,000 hospitalizations, 51,000 emergency department visits and more than 422,000 outpatient visits.

Griffin, the physician at Vanderbilt University Medical Center, said she was concerned that the vaccine was tested in a relatively healthy population in which hospitalizations were low, and there wasn’t any data on nursing home residents and people in frail health.

Akindele, the FDA official, said real-world evidence after a vaccine rollout could answer how much protection it provides for those in fragile health. The data would then be used to determine whether the FDA needs to make any adjustments to how the shot is used, she said.

Pfizer is conducting its clinical trial over two RSV seasons with more than 34,000 people enrolled. The available efficacy and safety data is from the first season.

When asked what would happen if data from the second season is not as strong after an approval, Akindele said the FDA would reevaluate the shot and meet with the committee again to determine how to proceed.

This is a developing story. Please check back for updates.



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