The anti-Covid vaccination still arouses reluctance, most of the time for fear of side effects. For allergy sufferers, there is no particular fear to have. Only allergy to certain excipients contained in vaccines, or allergy to the vaccine itself, may contraindicated vaccination. However, this type of reaction is very rare. "Less than one in 100,000 people is concerned," says Professor Frédéric Bérard, head of the allergology department at Lyon University Hospital and president of the College of Allergology Teachers. And even in the event of a reaction to a component of the vaccine, there are effective alternatives to protect against Covid-19.
Should we do an allergic assessment before being vaccinated against Covid-19?
In the vast majority of cases, this assessment is not necessary. Even people who have experienced severe episodes, such as anaphylactic shock following the ingestion of food or an insect bite, do not need to be tested before getting vaccinated.
What are the allergies that contraindicated the anti-Covid vaccination?
Two excipients can cause allergic reactions to Covid vaccination. These are on the one hand the polyethylene glycol (PEG) contained in messenger RNA vaccines (Pfizer and Moderna) and, on the other hand, the polysorbate found in the Covid vaccines of the AstraZeneca and Janssen laboratories (Johnson and Johnson).
How do you know if you are allergic to these excipients?
PEG is a molecule commonly used in cosmetics (creams, shampoos, hair dyes, etc.) and pharmaceutical products (laxatives, preparations for colonoscopy, etc.).
Polysorbate is also used in some injectable drugs and other more 'conventional' vaccines.
"These two excipients are usually poorly absorbed by the digestive tract, so reactions to a drug taken orally are exceptional. We, therefore, see allergies caused by injectable forms of drugs containing PEG or polysorbate," observes Dr. Bérard.
What happens if I become allergic to one of these excipients?
Specifically, a person who knows he is allergic to PEG or polysorbate must report it to his doctor or allergist before the first injection of the anti-Covid vaccine.
A skin test (a drop of the offending product is placed on the skin) will be performed in the hospital, under medical supervision. This test lasts less than an hour.
If the result is negative, 'the person can be vaccinated. You can even do the injection immediately on the spot," says Dr. Bérard.
If the test is positive, different solutions can still vaccinate the person:
- In case of allergy to PEG, messenger RNA vaccines (Pfizer and Moderna) are contraindicated. But it is possible to vaccinate with the AstraZeneca or Janssen vaccine, after checking that the person is not allergic to polysorbate.
- In case of allergy to polysorbate, AstraZeneca and Janssen vaccines are contraindicated. Vaccination with Pfizer or Moderna is offered, after verifying that the person is not allergic to PEG.
- What if the patient is allergic to both PEG and polysorbate? In this case (extremely rare), the doctor issues him a certificate of contraindication to the anti-Covid vaccination.
What happens in case of allergy after the 1st dose of Covid vaccine?
After the injection of the vaccine, it is advisable to remain under surveillance for a quarter of an hour. Indeed, the most severe reactions occur within minutes of vaccination.
If the patient develops adverse reactions that suggest that he or she is allergic to the vaccine, he or she will need to undergo allergological tests in a hospital setting before considering a second dose, which is necessary to obtain full vaccination coverage. From there, several situations are possible:
If the test is negative, this second injection is performed without changing the vaccine. As a precaution, the patient will be premeditated with an antihistamine drug before the booster injection. Everything happens in the hospital under close supervision," explains the allergist.
If the test is positive, the booster will not be carried out with this vaccine. It will then be possible to choose another vaccine that does not contain the allergen (after having performed skin tests before vaccination with this new vaccine). On the other hand, if all the tests are positive for the other vaccines, we will then issue a certificate of contraindication for the booster," says Professor Bérard.
In any case, whether vaccinated or not, barrier gestures such as wearing a mask and regular hand washing, remain essential to protect yourself and others from the Covid-19 epidemic.
Indeed, says the allergist, no vaccine protects 100% of the infection, but an overwhelming majority of vaccinated patients will at least be protected against the risk of severe form.
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