Pilot study of acute allergic reactions to mRNA-BNT162b2 vaccine in an ecuadorian cohort

ABSTRACT

Background: Allergic reactions to vaccines are rare, occurring at 1 per 1'000.000 to 30 per 100.000;BNT162b2 vaccine excipients include polyethylene glycol/macrogol (PEG), rarely cause of allergy. Contact sensitivity to PEG is more frequent than anaphylaxis. CDC reported an estimated rate of 11.1 cases of anaphylaxis per million doses administered in patients with a history of allergies. Method: We prospectively assessed the early allergic reactions of Phase 0 COVID-19 vaccination plan in Guayaquil, Ecuador. Participants received two 30-μg doses, administered intramuscularly 21 days apart. Phase 0 included first line health care workers who were healthy or had stable chronic medical conditions. Participants were observed for 30 minutes after vaccination for any acute reactions;we used Brighton scale for anaphylaxis definition criteria. The primary endpoint was to measure any allergic reaction, anaphylaxis and use of medication within 14 days after the receipt of each dose of vaccine;day 1 referred to the vaccination day. Participants reported their symptoms on weekly telephonic follow-up made by the pollsters team. Results: 187 subjects were enrolled, the mean age was 41.11 ± 17.78, 61% were female and 27.3% patients presented with an allergic past history, 15% had allergic rhinitis (Table 1). Allergic symptom onset was 2.2 ± 3.63 minutes compared to 30 minutes of another study. We did not report any anaphylaxis case. On the first day, 5.35% presented an allergic reaction including generalized rash, injection site rash and petechiae. On second dose, 3.7% presented injection site rash, generalized pruritus and petechiae (Figure 1). Conclusion: Our study found a similar prevalence of allergic reaction according to previous reports. The majority of patients, 94.65%, did not report any allergic symptoms after BNT162b2, similar to previous studies (98%). Anaphylaxis with COVID-19 vaccination is extremely rare, we did not find any case similarly to other reports (0.027%). To our knowledge, this is the first study to report acute allergic reactions in South America. Further studies are needed in order to prove the allergic reactions differences with other populations. (Table Presented).