Pfizer’s new RSV vaccine for older adults could cause the potentially deadly Guillain-Barre syndrome, the Food and Drug Administration (FDA) has warned.
In clinical trials, two participants in their 60s developed the condition, which can also cause crippling pain, muscle weakness, and paralysis.
One of the patients recovered after three months, but the second took six months to return to normal. They were among 20,000 adults who received the experimental injection.
There were no cases of GBS among the control group that did not receive the vaccine, prompting the FDA to ask Pfizer to conduct a safety review before approving the vaccine.
Several pharmaceutical companies are developing a vaccine against respiratory syncytial virus (RSV), a winter respiratory virus that kills up to 10,000 adults over 65 each year in the US. There is currently no injection against the disease available.
Guillain-Barre sees the immune system go haywire and nerve cells begin to attack, causing symptoms such as muscle aches, numbness, and tingling.
It was also registered during trials of a rival RSV vaccine made by British pharmaceutical giant GSK.
The condition has also been previously reported in people who received AstraZeneca’s Covid vaccine, which was not approved for use in the US.
One of the patients who developed the syndrome in Pfizer’s trial was an American man in his sixties with a history of high blood pressure.
Eight days after vaccination, he developed lower back pain and on the 14th day he felt weakness in his legs.
After a fall, the man was hospitalized and subsequently diagnosed with the syndrome. His symptoms disappeared in six months.
The patient also had a heart attack, but the FDA said it was not related to the RSV vaccine.
In the second case, a woman in her 60s in Japan with a history of type 2 diabetes developed a variant of the syndrome called Miller-Fisher syndrome.
Miller-Fisher tends to affect the upper body first, while Guillain-Barre usually affects the lower body and then spreads upward.
Nine days after the vaccination she was tired and on day ten she had a sore throat and poor muscle control.
She was hospitalized 19 days after vaccination. Her symptoms resolved within three months.
Official documents released by the FDA read: ‘Given the temporal association and biological plausibility, the FDA agrees with the investigators’ assessments that these events may have been related to the study vaccine.
‘Therefore, [Guillain-Barre] is seen as an important potential risk.’
Guillain-Barre is a rare neurological disorder in which the immune system malfunctions and begins to attack the nerves of the body.
In severe cases, it can cause paralysis, difficulty breathing, blood clots, and death. It can also cause patients to suffer pain.
It normally appears within days or weeks of a respiratory or digestive tract infection. Previous research has linked both Covid and RSV infections to the syndrome and previous vaccines.
There is no cure for the syndrome, but treatments are available that can speed recovery.
About one to two Americans per 100,000 people have Guillain-Barre syndrome, estimates suggest. This rises to one in 33,000 people over the age of 60.
The documents were released ahead of a meeting to approve the vaccine next week, led by the Vaccines and Related Biological Products Advisory Committee (VRBPAC) — which reviews vaccine safety and effectiveness.
Pfizer has agreed to conduct the safety assessment of its phase three clinical trial, the final phase before approval.
But in a briefing paper, the company suggested there may be other explanations for the reactions.
They add that the injection is a “well-tolerated and safe vaccine, with a favorable benefit-risk ratio.”
There is currently no vaccine available against RSV, which peaked this winter in the absence of Covid restrictions.
RSV is a common infection that causes cold symptoms that go away in a few days.
But it is more dangerous in older adults who have weaker immune symptoms and can cause pneumonia and even death in severe cases.
The phase three clinical trials showed that Pfizer’s jab was 66.7 percent effective in preventing moderate lower respiratory tract disease with two or more symptoms.
It was also 85 percent effective in preventing serious illness.
This was similar to the injection developed by GSK, which was 94.1 percent effective against serious lower respiratory tract disease and 82.6 percent effective in preventing disease in general.
Cases of possible Guillain-Barre syndrome were also recorded in this study, but there was not enough evidence to confirm a diagnosis.
Data from both vaccines were discussed Thursday at a meeting of the CDC’s Advisory Committee on Immunization Practices.
They concluded that the vaccines showed “significant efficacy against lower respiratory tract disease caused by RSV in older adults.”
But they added that “post-licensing surveillance for both the safety and effectiveness of the vaccine will be critical” if the jabs are approved by the FDA.
Leave a Reply