We agree that great consideration needs to be given to the possibility that the polyethylene glycol [PEG])-2000]-N,N-ditetradecylacetamide micellar carrier system for the active mRNA spike protein component of the Pfizer–BioNTech BNT162b2 mRNA vaccine, sometimes referred to as the lipid nanoparticle (LNP) delivery system, could be evoked in the recent immediate reactions post-emergency use authorization (EUA).
In our prior work, we have described patients with immediate reactions to PEG3350. These reactions were consistent with anaphylaxis to PEG3350 bowel preparations and corticosteroids containing both PEG3350 and polysorbate (PS) 80 as an excipient.
[O]ur clinical and laboratory observations do support that IgE-mediated reactions can occur to a PEG-containing product presumably due to previous subclinical sensitization. These patients can notably be labeled as “idiopathic anaphylaxis” or multiple drug allergy if multiple episodes to different products occur over time without knowledge of the shared excipients.
[F]or immediate reactions associated with PEG there appears to be a molecular weight (MW) threshold.
[We saw] patients who were positive to PEG3350 but negative to PEG300 who then tolerated oral challenge with PEG300.
[W]e have observed increasing binding avidity of anti-PEG sIgG as the molecular weight of the PEG increases.
PEG2000 is crucial to the formation of micelles used as the delivery system for the mRNA vaccines.
Cases clinically compatible with anaphylaxis to the Pfizer–BioNTech mRNA vaccine have occurred on the first dose in the post-EUA phase of surveillance in healthcare workers.
It is possible that these could be IgE-mediated reactions related to preexisting sensitization to a different PEG product.
Until we understand more, patients with previous immediate reactions compatible with PEG anaphylaxis will be excluded from receiving the SARS-CoV-2 mRNA vaccines.
Until assessed by an allergist, it would be recommended that these individuals also avoid not only future vaccination with an mRNA SARS-CoV-2 vaccine but all components of the vaccine which would include PEG products.