Two Cases of Rare Neurological Disorder Seen After Pfizer RSV Vaccine Administration

Ahead of the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) meetings tomorrow and Wednesday, filing documents showed 2 cases of Guillain-Barre syndrome (GBS) developed shortly after Pfizer’s investigational RSVpreF (Abysvo) RSV vaccine was administered.

The committee is meeting tomorrow to discuss and make recommendations on the safety and effectiveness of the company’s vaccine with regards to its BLA for active immunization for the prevention of acute respiratory disease and lower respiratory tract disease (LRTD) caused by respiratory syncytial virus in adults 60 years of age and older.

In the accompanying FDA briefing document, 2 cases of GBS were explained in detail, and here is the case information of each:

• A 66-year-old male with a past medical history of hypertension developed GBS, graded as life-threatening in severity, with onset of symptoms 7 days after receipt of RSVpreF. Prior to the onset of these symptoms, the participant had experienced a non-ST elevation myocardial infarction, not considered related to vaccination, on Day 7. He was hospitalized on Days 7-8 for cardiac catheterization and angioplasty and on Day 8 developed lower back pain. On Day 14, he developed bilateral lower extremity weakness, and due to a fall, he was hospitalized. Physical exam and laboratory findings were consistent with the diagnosis of GBS. He was treated with intravenous immune globulin, and 5 sessions of plasmapheresis. Symptoms improved and the event of GBS was resolving at the time of the last available report, approximately 6 months after symptom onset.

• A 66-year-old female with a past medical history of type 2 diabetes mellitus developed Miller Fisher syndrome, graded as severe, with onset 8 days after receipt of RSVpreF. The participant reported fatigue on Day 9, sore throat on Day 10, and ataxia on Day 11. On Day 19, she was hospitalized for severe fatigue and unstable movements, and later developed diplopia, ataxia, and paresthesia of bilateral palms and soles. Ophthalmoplegia was seen on exam. Her symptoms started to resolve on Day 40, without treatment. On Day 41, she was retrospectively diagnosed with Miller Fisher syndrome based on clinical course. The participant’s symptoms resolved completely approximately 3 months after symptom onset.
  
  

“For all of the cases listed above, the event was assessed as possibly related to study vaccine by the investigators but assessed as unrelated by the applicant,” as written in the briefing document. “Given the temporal association and biological plausibility, FDA agrees with the assessments of the investigators that these events were possibly related to study vaccine.”

According to the CDC, an estimated 3000 to 6000 Americans develop GBS annually. The federal agency also notes there are several factors that can lead to GBS, and these include:

Diarrhea/Respiratory Illness. About 2 in every 3 people with GBS had diarrhea or a respiratory illness several weeks before developing GBS symptoms.

Viral infections. Some people with GBS had the flu or infections with cytomegalovirus, Epstein Barr virus, Zika virus, or other viruses.

Vaccination. Very rarely people have developed GBS in the days or weeks after getting certain vaccines. However, benefits of vaccination far outweigh risks. For example, studies show that people have a greater chance of getting GBS after getting the flu than they do after getting vaccinated against the flu.

It is important to note this adverse event is extremely rare, 2 people out of over 19,000 individuals in the Pfizer trials developed GSB, and both individuals have had these adverse events resolved.

Pfizer Data
Pfizer received Breakthrough Therapy Designation for their RSV vaccine last March. The company, last September, reported its topline data from its phase 3 RENOIR trial which demonstrated an efficacy of 85.7% in participants with a more severe disease primary endpoint of lower respiratory tract illness (LRTI-RSV).

The RENOIR trial was a global, randomized, double-blind, placebo-controlled study designed to assess the efficacy, immunogenicity, and safety of a single dose of RSVpreF in adults 60 years of age and older. The trial enrolled approximately 37,000 participants, randomized to receive 120μg RSVpreF or placebo in a 1:1 ratio.

This week’s VRBPAC meetings information and resources can be found here.