About 1% of the entire population is allergic to aspirin.
Consider this. An over the counter medicine is sold without prescription having 1% of the population allergic to it. That is 1 in 100. Omontys negative reaction has been 1 in 1000. 0.1% and mostly mild cases. So the severe allergic reactions are for most likely, less than 0.05% since the vast majority of that 0.1% allergic have only mild issues.