Should I stay or should I go? Observation post-vaccination during the COVID-19 pandemic and the law of unintended consequences

Background Standard practice after all vaccinations in Australia is to observe patients for 15 minutes. During the COVID-19 pandemic, could the risk of contracting and dying from COVID-19 acquired in the waiting room be greater than the risk of dying from post-vaccine anaphylaxis when leaving immediately? Methods The risks are modelled for a patient aged 70+ years attending for annual influenza vaccination in a typical Australian general practice clinic. The risk of death from anaphylaxis is estimated based on known rates of anaphylaxis shortly after influenza vaccination. The risk of acquiring COVID-19 during a 15-minute wait and then dying from that infection is estimated using the COVID-19 Aerosol Transmission Estimator and COVID-19 Risk Calculator. Results Other than at times of extremely low COVID-19 prevalence, the risk of death from anaphylaxis for a patient aged 70+ years leaving immediately after influenza vaccine is less than the risk of death from COVID-19 acquired via aerosol transmission during a 15-minute wait. The risk of death from COVID-19 is greatest for the unimmunised and when masks are not worn. Conclusions A more nuanced approach to advice post-vaccination is recommended that considers current COVID-19 prevalence and virulence, the characteristics of the waiting room, the risk of anaphylaxis, and the patients susceptibility to death from COVID-19. There are many circumstances where it would be safer for a patient to leave immediately after vaccination