Data continue to show COVID-19 revaccination safe for patients following initial reaction

Key takeaways:

• 51.7% of the patients who were referred to allergy centers due to experiencing an immediate adverse event after COVID-19 vaccination did not meet the case definition for anaphylaxis.
• 95.6% of the cohort was able to be revaccinated safely, with only 4.3% developing objective signs of a possible immune adverse event following immunization.
• Skin testing was not useful in predicting challenge positivity.

Patients who have an adverse event immediately after COVID-19 vaccination can be revaccinated if they are selected carefully and challenged in a supervised environment, according to a letter published in Allergy.

The study also is one of the first to report outcomes for challenges to the ChAdOx1-S (recombinant; Vaxzevria, AstraZeneca/Oxford) vaccine, Joseph Francis De Luca, MD, a PhD candidate in the department of medicine at University of Melbourne in Australia, and colleagues wrote in the letter.

The retrospective, multicenter cohort study involved 116 adults (93.1% women; median age, 45.2 years; interquartile range, 35.75-56.23) who were referred to two allergy centers after they had adverse events immediately after receiving the BNT162b2 (Pfizer-BioNTech) or ChAdOx1-S vaccines between April and August 2021. Two of the patients (1.7%) had been infected with SARS-CoV-2 before.

At least one dose of adrenaline was administered to 68 of the patients (58.6%). Also, 60 patients (51.7%) did not meet the Brighton collaboration criteria for anaphylaxis, whereas 11.2% met level 1 criteria, 34.5% met level 2 and 2.6% met level 3.

Next, 23 patients (19.7%) had skin testing with polyethylene glycol and polysorbate 80 panels, and all were negative.

Also, 45 patients (38.7%) had a positive challenge to the vaccines, including 18 (40%) for ChAdOx1-S and 27 (60%) to BNT162b2. Forty of these patients had mild and subjective reactions, and five had objective signs of reactions, four of whom did not meet Brighton criteria for anaphylaxis, with the fifth meeting level 1 criteria. Two patients received adrenaline after experiencing rash and throat tightness with normal vital signs.

Multivariable analysis revealed that absence of a history of atopy (OR = 8.13; 95% CI, 1.66-39.7), absence of hospitalization (OR = 2.89; 95% CI, 0.97-8.66) and any treatment for the index reaction (OR = 6.06; 95% CI, 1.46-25.16) were predictors of positive challenge.

Patients who experienced Brighton level 1 anaphylaxis (OR = 7.27; 95% CI, 1.52-34.66) or who did not meet the case definition for anaphylaxis (OR = 3.06; 95% CI, 1.01-9.34) in their index reactions also were more likely to have positive challenges than patients categorized with Brighton level 2 or 3 anaphylaxis in their index reactions.

Overall, given that 61.2% of the cohort had a negative vaccine challenge and 34.4% only had mild, subjective symptoms following the challenge, the researchers found that 95.6% of the cohort could be revaccinated safely with only 4.3% developing objective signs of a possible immune adverse event. The researchers called these results consistent with international experience.

Further, the researchers said that skin testing was not useful for predicting challenge positivity. There also was no association between increased risk for positive challenge and atopy or hospitalization, indicating that patients at risk for positive challenge lack classical allergy phenotypes, the researchers wrote.

Although the patients who did not meet Brighton criteria for anaphylaxis had a higher risk for a positive challenge, the researchers continued, these reactions might not be immune-mediated, explaining why patients with severe reactions still tolerated challenges.