COVID-19 vaccines: New concepts for high-risk patients

Since the first anaphylactic reactions after injection of the COVID-19 vaccines, studies on side effects and severe allergic events have been ongoing worldwide. Now there are also first results on a successful premedication scheme and vaccination concepts for high-risk patients.

Allergies and anaphylaxis: no absolute contraindication with appropriate premedication

Since the first anaphylactic reactions after injection of the COVID-19 vaccines, studies on side effects and severe allergic events have been ongoing worldwide. Now there are also first results on a successful premedication scheme and vaccination concepts for high-risk patients.

Women are more often affected by allergic vaccination reactions than men

People with a history of known allergies and anaphylactic events have a special context with regard to COVID-19 vaccinations. Against this background, various studies are currently being conducted on the actual risk for those affected, and the possible risk factors. The results of a recent American study show that the risk of allergic and anaphylactic reactions was on average higher in women than in men. Overall, allergic events occurred in about 2% of patients - on average more with the Moderna vaccine than with the Pfizer/BioNTech vaccine.

Anaphylactic reactions occurred in 0.025% of participants, again slightly more after the Moderna vaccine compared to the Pfizer/BioNTech vaccine. The average age of those affected with such events was 41 years. 94% of those affected were female. Of these, 63% had a history of allergic reactions and 31% had a history of anaphylactic reactions. On average, 17 minutes passed until the onset of the events. Late reactions were also observed; these were mostly erythematous skin changes that were self-limiting after a few days.

Elevated tryptase levels in patients with allergic reactions

It was shown that elevated tryptase levels (> 7.5 ng/ml) could be an indication of an increased risk for anaphylactic reactions. Mast cell disorders, on the other hand, are not a risk factor, contrary to the original hypothesis. In a study with 51 patients with different mast cell disorders, it was shown that the majority of patients tolerated the COVID-19 vaccines well. Overall, only few side effects occurred.

Case study: Patient successfully vaccinated despite anaphylaxis

The question arises as to how to proceed with patients who experience anaphylactic reactions after the first vaccination. In this context, the Harvard Medical School in the USA presented a first successful vaccination regime in the following patient:

• Male patient, 40 years old, from Iran, no known allergies to drugs or vaccines.
• Known food allergy to various seafood products, first manifestation at age 11 years with generalised pruritus, facial and laryngeal oedema, treated with epinephrine in the emergency department.
• Thereafter three further episodes, the last in 2019, following accidental consumption of fish products, same treatment and recommendation of consistent avoidance of seafood and fish.

Then, on 24 December 2020, the vaccination of the first dose of the Moderna vaccine took place:

• Within 2-3 minutes development of generalised pruritus, swelling of larynx and tongue, hypotension, presyncope.
• Treatment with self-injection (Epipen) followed by emergency admission and further epinephrine injection, normalisation of the condition after 6 hours.

• 24 hours after initial event: late reaction with fatigue, palpitations, generalised pruritus and laryngeal oedema - treatment with H1 antihistamines and fluid substitution.

Before administration of the second dose of Moderna vaccine, pre-treatment was given according to a new pre-medication regimen:

• 12 hours before vaccination: cetirizine 10 mg, famotidine 20 mg, montelukast 10 mg
• 1 hour before vaccination: cetirizine 10 mg, famotidine 20 mg, montelukast 10 mg. 
• The vaccination was administered in three steps:
  • 1st step 0.1 ml
  • 2nd step 0.15 ml
  • 3rd step 0.25 ml

The patient did not experience any allergic side effects after the second dose and could be discharged home successfully vaccinated.

Conclusion on anaphylactic reactions after COVID-19 mRNA vaccines:

• anaphylactic reactions are rare (1/100.00-200.00)
• Women are affected more often than men
• Epinephrine is currently the only effective therapy
• Elevated tryptase levels in patients with allergic reactions
• Allergies, history of anaphylactic reactions or mast cell disorders are not absolute contraindications to vaccination.
• Premedication should be considered in patients at risk.
• Premedication can effectively prevent severe reactions

Source:
Prof. Castells, Mariana, Harvard Medical School in the United States, APAAACI Online-Symposium 11, Risk and Safety of COVID Vaccines, October 2021