Patients with previous immediate hypersensitivity reactions to polyethylene glycol can safely receive the BNT162b2 mRNA COVID-19 vaccine.

Previous anaphylaxis or immediate allergic reaction to polyethylene glycol (PEG; also known as macrogol) is considered a contraindication to the BNT162b2 mRNA COVID-19 vaccine, which contains 50 ug of PEG at a molecular weight of 2000, and this component is thought to account for the higher rate of anaphylaxis seen with this vaccine (4.7 per million doses) than with other non-mRNA vaccines. However, there is evidence that both anaphylaxis to PEG and anaphylaxis to the Pfizer COVID-19 reaction may not be IgE-mediated, with patients with anaphylaxis to first dose of the Pfizer COVID-19 vaccine receiving their second dose of vaccine without no or milder reactions in a high-risk clinic setting. In New Zealand, non-PEG-containing COVID-19 vaccines were not available until late 2021. Therefore, we offered patients with known or suspected PEG anaphylaxis their first dose of Pfizer COVID-19 vaccine in a high-risk hospital clinic. Eleven patients with previous hypersensitivity to PEG (including eight with anaphylaxis) successfully received their first dose with mild or no reactions; all have now had their second doses in the community without significant reaction. Record review also showed that most patients with previous hypersensitivity reactions to pegylated asparaginase have also been successfully vaccinated. This demonstrates that previous PEG hypersensitivity, including anaphylaxis, does not exclude immunisation with the Pfizer COVID-19 vaccine.

Penicillin Allergy De-labeling Results in Significant Changes in Outpatient Antibiotic Prescribing Patterns.

Unverified penicillin allergies are common but most patients with a penicillin allergy label can safely use penicillin antibiotics. Penicillin allergy labels are associated with poor clinical outcomes and overuse of second-line antibiotics. There is increasing focus on penicillin allergy "de-labeling" as a tool to improve antibiotic prescribing and antimicrobial stewardship. The effect of outpatient penicillin allergy de-labeling on long-term antibiotic use is uncertain. We performed a retrospective pre- and post- study of antibiotic dispensing patterns, from an electronic dispensing data repository, in patients undergoing penicillin allergy assessment at Auckland City Hospital, New Zealand. Over a mean follow-up of 4.55 years, 215/304 (70.7%) of de-labeled patients were dispensed a penicillin antibiotic. Rates of penicillin antibiotic dispensing were 0.24 (0.18-0.30) penicillin courses per year before de-labeling and 0.80 (0.67-0.93) following de-labeling with a reduction in total antibiotic use from 2.30 (2.06-2.54) to 1.79 (1.59-1.99) antibiotic courses per year. In de-labeled patients, the proportion of antibiotic courses that were penicillin antibiotics increased from 12.81 to 39.62%. Rates of macrolide, cephalosporin, trimethoprim/co-trimoxazole, fluoroquinolone, "other" non-penicillin antibiotic use, and broad-spectrum antibiotic use were all lower following de-labeling. Further, antibiotic costs were lower following de-labeling. In this study, penicillin allergy de-labeling was associated with significant changes in antibiotic dispensing patterns.