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Allergy to Covid-19 Vaccines

Dr. Pedro Morais Silva, Immunoalergologist


Regarding the risk of developing an allergic reaction, what are the current contraindications for administering the currently available SARS-CoV-2 vaccines?

According to the current Clinical Guidelines of the DGS, the following are considered contraindications: a) a history of a known allergy to one of the vaccine excipients to be administered or b) a history of anaphylaxis to a previous vaccination against the SARS-CoV- virus two.

These patients must be referred, with urgent priority, to an immunoallergy service, in order to be evaluated for risk stratification and possible alternatives to be studied.

In addition, patients with a previous history of: a) anaphylactic reactions to other vaccines (non-SARS-CoV-2); b) patients with a history of idiopathic anaphylaxis; c) patients with confirmed allergy to excipients (even if not present in the SARS-CoV-2 vaccines) and d) patients with systemic mastocytosis or mast cell proliferative diseases. 

Are allergic reactions to COVID-19 vaccines common?

No. These are estimated to occur in less than 1 in 10,000 administrations. However, as with any medicine, vaccines can trigger unwanted effects, which are sometimes incorrectly interpreted as allergy. The most common adverse effects include injection site reactions, headache, muscle or joint pain, fever, feeling tired, feeling sick and feeling unwell. None of these symptoms are due to an allergic reaction and usually resolve spontaneously within 3 days.


Can a patient allergic to penicillin or anti-inflammatory drugs be vaccinated?

Yes. Allergy to penicillin or other beta-lactams and anti-inflammatory drugs is not a contraindication to the administration of currently available vaccines.


Can patients with severe food allergies be vaccinated?

Yes. After reviewing cases of allergy related to the administration of vaccines against the SARS-CoV-2 virus, no relationship with food allergy was identified.


Some vaccines are contraindicated in patients with egg allergy. Do vaccines contain egg proteins?

No. Pfizer/BioNTech, AstraZeneca, Johnson & Johnson and Moderna vaccines do not contain egg proteins.


Can patients allergic to mites or pollens receive the vaccine against the SARS-CoV-2 virus? And can patients who are undergoing allergen immunotherapy (“allergy vaccines”) be vaccinated?

Yes. Allergy to respiratory allergens is not a contraindication for any of the vaccines. Likewise, patients undergoing immunotherapy with aeroallergens can be vaccinated, with at least one week difference between vaccination against SARS-CoV-2 and administration of immunotherapy, as well as any other vaccine, being advised.


Are patients with asthma at higher risk of having a reaction to a SARS-CoV-2 vaccine?

No. However, as with other vaccines, it is recommended that asthma be controlled at the time of vaccination.


Can patients with compromised immunity receive the vaccine?

mRNA and adenovirus vector vaccines are not live vaccines and cannot cause infection. For this reason, they are globally considered safe for administration in immunocompromised patients. However, depending on the underlying pathology, some patients may have a diminished immune memory response to vaccines.




8, June 2021