Health officials are looking into cases of Guillain-Barre syndrome following RSV vaccination.
Newly developed RSV vaccines from Pfizer and GlaxoSmithKline show higher-than-expected rates of GBS, suggesting a possible risk associated with these vaccines.
Recently the CDC has provided preliminary analysis regarding the recently released respiratory syncytial virus vaccines and a possible association with the rare neurological condition called Guillain-Barre syndrome, or GBS.
The causes of GBS are not entirely known, but it appears to be a phenomenon in which the immune system may target peripheral nerve cells, generally resulting in the manifestation of muscle weakness as a main symptom.
As for RSV, the virus is seasonal and generally mild disease for most individuals, usually presenting with cold-like symptoms. Although research has been looking into RSV vaccines for decades, it wasn’t until last year that two vaccines against RSV were approved:
Pfizer’s ABRYSVO (aka RSVPreF)
GlaxoSmithKline’s AREXVY (aka RSVPreF3+AS01)
As of now the available RSV vaccines have been marketed towards those over the age of 60 predominately as they are argued to be the most at-risk of developing severe illness. And so far over 2 million doses in total appear to have been administered in approved countries. Unlike the COVID vaccines the RSV vaccines available are administered as a single dose.
The comments regarding GBS come after the FDA released preliminary data from a presentation, in which it was noted that both vaccines appear to show a higher than expected rate of GBS cases within 42 days of receiving an RSV vaccine.
Interestingly, the observed events of GBS appear higher among those who received Pfizer’s vaccine. Even though recipients of ABRYSVO make up only 1/3 of RSV vaccine recipients, they also account for more than half of the reported cases of GBS.
Now, the rates of GBS still appear relatively low with overall cases between the vaccines being around the low 20s, but the fact that rates appear elevated nonetheless pose questions as to what may be occurring.
The current evidence is somewhat confounded, as most RSV vaccine recipients are far older than the general population. It’s been suggested that the risk of GBS increases with age which may factor in to the increased risk seen, with age-stratification showing a higher number of reported cases of GBS. How this may relate to the higher possible risk among older population is still left to be determined.
Given that Pfizer’s vaccine shows higher reported cases with fewer vaccines administered, there may be something regarding the formulation of Pfizer’s vaccine which may provide some insights.
However, when comparing the package inserts there doesn’t appear to be egregious differences between Pfizer and GSK’s formulations. Both, for the most part, utilize the surface F glycoprotein of RSV in their formulations, and thus are protein subunit-based vaccines.
Pfizer’s vaccine appears to use F glycoproteins from two different strains of RSV. As for GSK the source of the F glycoprotein isn’t as clear.
A greater description for the two vaccines are as follows (derived from corresponding vaccine package inserts):
ABRYSVO (Respiratory Syncytial Virus Vaccine) is a sterile solution for intramuscular injection. The vaccine is supplied as a vial of Lyophilized Antigen Component that is reconstituted at the time of use with a Sterile Water Diluent Component. The antigen component contains recombinant RSV preF A and RSV preF B.
The RSV preF A and RSV preF B recombinant proteins are expressed in genetically engineered Chinese Hamster Ovary cell lines grown in suspension culture using chemically-defined media, without antibiotics or animal-derived components. The recombinant proteins are purified through a series of column chromatography and filtration steps followed by formulation, filling into vials, and lyophilization.
After reconstitution, each dose of ABRYSVO is approximately 0.5 mL. The vaccine is formulated to contain 120 mcg of RSV stabilized prefusion F proteins (60 mcg RSV preF A and 60 mcg RSV preF B) per 0.5 mL. ABRYSVO also contains the following buffer ingredients: 0.11 mg tromethamine, 1.04 mg tromethamine hydrochloride, 11.3 mg sucrose, 22.5 mg mannitol, 0.08 mg polysorbate 80, and 1.1 mg sodium chloride per 0.5 mL. ABRYSVO is a sterile, clear, and colorless solution.
ABRYSVO contains no preservatives. Each dose may also contain residual amounts of host cell proteins (≤0.1% w/w) and DNA (<0.4 ng/mg of total protein) from the manufacturing process.
AREXVY (Respiratory Syncytial Virus Vaccine, Adjuvanted) is a sterile suspension for intramuscular injection. The vaccine is supplied as a vial of lyophilized recombinant respiratory syncytial virus glycoprotein F stabilized in pre-fusion conformation (RSVPreF3) as the antigen component, which must be reconstituted at the time of use with the accompanying vial of AS01E adjuvant as the adjuvant suspension component.
The RSVPreF3 antigen is expressed by culturing genetically engineered Chinese Hamster Ovary cells in media containing no antibiotics or animal-derived proteins. The RSVPreF3 protein is purified by several chromatographic and filtration steps, formulated with excipients, filled into vials, and lyophilized.
The AS01E adjuvant is composed of 3-O-desacyl-4’-monophosphoryl lipid A (MPL) from Salmonella minnesota and QS-21, a saponin purified from plant extract Quillaja saponaria Molina, combined in a liposomal formulation. The liposomes are composed of dioleoyl phosphatidylcholine (DOPC) and cholesterol in a phosphate-buffered saline solution containing disodium phosphate anhydrous, potassium dihydrogen phosphate, sodium chloride, and water for injection.
After reconstitution, each 0.5-mL dose is formulated to contain 120 mcg of the recombinant RSVPreF3 antigen, 25 mcg of MPL, and 25 mcg of QS-21. Each dose also contains 14.7 mg of Trehalose, 4.4 mg of sodium chloride, 0.83 mg of potassium dihydrogen phosphate, 0.26 mg of dipotassium phosphate, 0.18 mg of polysorbate 80, 0.15 mg of disodium phosphate anhydrous, 0.5 mg of DOPC, and 0.125 mg of cholesterol. AREXVY contains no preservative. '
Each dose may also contain residual amounts of host cell proteins (≤2.0%) and DNA (≤0.80 ng/mg) from the manufacturing process.
One distinction could relate to the use of a saponin in GSK’s vaccine formulation which appears similar to that of Novavax’s SpikeVax COVID vaccine, in which case it may suggest that GSK’s vaccine presents the F glycoprotein on the surface of liposomes likely mimicking the structure of an RSV virion.
This may suggest that presentation of F glycoprotein may be different between the two RSV vaccines, and thus may be related to the increased risk of GBS among Pfizer recipients, although this is merely a speculation.
Thus, although GBS appears rather rare in both vaccines their higher-than-expected incidences nonetheless raise questions regarding what may be influencing this increased risk. Given that both vaccines utilize protein subunits the answer for the differences in reported adverse events may lie somewhere else in the formulation or purification of these products, although there are likely to be differences among the subunits used as well.
And so more important than the fact that GBS cases are being reported is the explanation for why this may be higher among Pfizer vaccine recipients, and what differences in formulation or patient demographics may help to provide more context.
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Pfizer made a vaccine with a severe side-effect? I'm shocked! Shocked!
(Will we ever stop this madness?)
Just throw it on the pile of reasons I will never take another vaccine, or give one to my kids.