First data from Vaccine Allergy Safety clinics reaffirm COVID-19 vaccine safety

First data from Vaccine Allergy Safety (VAS) clinics in Hong Kong show that a majority of high-risk patients can receive coronavirus disease 2019 (COVID-19) vaccination safely, with no immediate allergic reactions.

The data also support the removal of history of anaphylaxis to non–COVID-19 vaccine or associated excipients as a precaution to COVID-19 vaccination. The high rates of inappropriate VAS clinic referrals and inaccurate diagnoses of anaphylaxis shown in the study, as well as inability to diagnose excipient allergies, may represent barriers to vaccination uptake. [World Allergy Organ J 2022;15:100622]

COVID-19 VAS clinics have been established in the Hospital Authority’s Hong Kong West Cluster (HKWC) and the Hong Kong Sanatorium & Hospital (HKSH) to provide allergist assessment to patients deemed to be at higher risk of COVID-19 vaccine–associated allergic reactions.

Among the first 1,127 patients (median age, 49 years; male, 33.6 percent; pre–COVID-19 vaccine referrals, n=1,018; post–COVID-19 vaccine referrals, n=109) evaluated between February and June 2021, 97.8 percent (n=1,102) were deemed not to be clinically compatible with vaccine or excipient-associated allergies after complete allergist evaluation. These patients were recommended to proceed with vaccination.

Among patients recommended for vaccination, more than 80 percent (n=450/558) of those who could be contacted subsequently confirmed that they had received COVID-19 vaccination successfully, with no immediate allergic reactions.

Only 2.4 percent of patients (n=25; pre–COVID-19 vaccine, n=24; post–COVID-19 vaccine, n=1) were recommended to defer COVID-19 vaccination. This was predominantly (n=21/24 [87.5 percent] of pre-vaccine patients) due to inability to confidently exclude possible excipient allergies based on prior history of multiple suspicious drug reactions, as excipient lists are not mandatory for product inserts of drugs registered in Hong Kong.

In addition, one post–COVID-19 vaccine patient was diagnosed with BNT162b2 anaphylaxis and was recommended to complete vaccination with the inactivated CZ02 vaccine as an alternative.

The results also revealed a high proportion of inappropriate VAS clinic referrals, determined based on guidelines of the Department of Health (DH) and Hong Kong Institute of Allergy (HKIA). Following commencement of pre–VAS clinic referral screening in the public sector since June 2021, 45.1 percent of referrals (n=1,133/2,514) to the HKWC VAS clinic were identified as inappropriate due to insufficient information or incorrect indications for referral.

Surprisingly, 56.2 percent (n=100/178) of patients referred to the HKWC VAS clinic due to history of suspected anaphylaxis did not meet the National Institute of Allergy and Infectious Disease and Food Allergy and Anaphylaxis Network (NIAID/FAAD) diagnostic criteria for anaphylaxis. Among those with confirmed anaphylaxis (43.8 percent; n=78/178), the most common aetiology was exercise-induced or food-dependent anaphylaxis (20 percent).

“Extrapolating inappropriate referrals and incorrect diagnoses of anaphylaxis alone, more than half of all patients referred to [the HKWC] VAS clinic in June 2021 could have been directly vaccinated without the need for prior allergist evaluation,” the researchers pointed out.

“Notably, there was no association between having a prior history of suspected anaphylaxis or history of multiple drug allergies with recommendation for COVID-19 vaccination,” they noted.

The researchers thus recommended updating the HKIA and DH guidance to remove anaphylaxis to non–COVID-19 vaccine or related excipients as a precaution for COVID-19 vaccination, consistent with recent updates in UK’s and Singapore’s guidelines. “Only a history of COVID-19 vaccine–associated anaphylaxis should be kept as a precaution,” they emphasized.

“There should be closer collaboration between primary care physicians and allergy specialists with a focus on improving allergy training for front-line doctors,” they added. “[In addition,] full excipient lists for all registered drugs should be mandated in Hong Kong as soon as possible.”