It is important to understand the initial “scare” that led to the now misunderstood idea that persons with history of allergy should not receive Covid-19 vaccine. First is that the reports of allergic reactions occurred in UK during their initial roll out of the Pfizer Covid-19 vaccine in which 2 individuals developed anaphylaxis after receiving the Covid-19 vaccine and had a history of requiring Epipen. This led to the UK regulators issuing an advisory statement which listed prior anaphylaxis to vaccines, medicine or food as a contraindication to receiving the vaccine. However the US FDA and CDC did not issue such a statement. After further surveillance gave reassurance of the vaccine safely, the UK regulator lifted the contraindication 3 weeks later. However, we still mistakenly refer to this allergy contraindication.
It is important to note that the reports of anaphylaxis are limited so far to the Pfizer and Moderna vaccines, both of which utilize the mRNA vaccine model delivered through pegylated lipid nanoparticles. The process of pegylation prevents enzyme degradation of the mRNA and also increases water solubility of the particle thus improving delivery of the mRNA. The current thought process is that the allergic reactions that we are seeing are reactions to the PEG found in these mRNA vaccines. This PEG molecule known as polyethylene glycol or Macrogol is used in a lot of medicinal, cosmetic and household products. Reports of allergy to PEG is very rare, thus the very low prevalence of PEG allergy looks to be inconsistent with the number of initial cases of anaphylaxis reported to the Pfizer-BioNTech vaccine. We would also have seen association of the vaccine reactions to individuals with PEG allergy. Therefore we must still consider other potential triggers or mechanisms for the reported reactions. Research is underway to find out exactly what is the underlying mechanisms triggering the allergic reactions.
It is important to understand that vaccinations can cause severe allergic reactions. Here are some data to allow you to understand the frequency of allergic reactions to vaccines:
- Among the first 22 million doses of Covid-19 vaccine administered in the United States, anaphylaxis has been extremely rare. As of January 18, 2021, and as part of the VAERS data presented to the Advisory Committee on Immunization Practices, the rate of anaphylaxis to the Pfizer vaccine was 5 per million doses and 2.5 per million for Moderna.
- Rates of anaphylaxis for most other vaccines, occurs at a rate of less than 1 per million doses.
Thus the severe allergic reactions to vaccines in general are quite low. The risk benefit ratio will lean towards benefit from vaccination.
The current recommendations for Covid-19 vaccination are as follows
- All Covid-19 vaccines should be administered in a facility where each person can be monitored for at least 15 minutes with treatment readily available for anaphylaxis. Anyone with a history of non-anaphylactic reactions to food, oral medication, latex, environmental, or venom allergens can safely receive either the Pfizer or Moderna vaccine in this manner.
- Anyone with a history of anaphylaxis to food, oral medication, latex, environmental, or venom allergies can receive either the Pfizer or Moderna vaccine without any precautions other than a recommended 30-minute observation period.
- Anyone with a history of immediate onset hypersensitivity reactions (urticaria, wheezing, angioedema, anaphylaxis) to any prior vaccine or injected medication can receive either the Pfizer or Moderna vaccine with a recommended 30-minute observation period. Consultation with an allergist to discuss risks/benefits may also be considered.
- Anyone with known and proven IgE mediated reactions to PEG or polysorbate are currently advised to avoid the Pfizer and Moderna vaccines. Given the rarity of allergies to these ingredients, it is unlikely for anyone to have this known allergy, unless specifically evaluated by a board certified allergist/immunologist and confirmed with prior skin testing.
If you have any concerns or questions about vaccination, please discuss it with your healthcare professional who can then perform a proper thorough evaluation of your history to give you the best medical advice. Please bear in mind that the Pfizer and Moderna Covid-19 vaccines are not the only vaccines available, your healthcare provider may choose an alternative more suitable vacccine for you.
