In the United States, corona vaccinations are very low-threshold and are also administered, for example, in supermarkets or even at gas stations. For flight personnel, whose turn is not yet theirs in many European countries, it would be tempting to get them during a work-related stay in the USA. Aer Lingus warns against this in a circular.
In some US states, cash bonuses are even paid for getting vaccinated. Much is not questioned, because pretty much everyone who shows up at a vaccination center also gets injected with a vaccine. Accordingly, for crews who have to spend the night in the United States due to circulation, it would be a small thing to get vaccinated quickly and easily. This is largely possible without any problems.
However, Aer Lingus warns against this in an internal circular. Under no circumstances should you get vaccinated during business stopovers in the USA. The crews are even clearly informed that they are expressly prohibited from vaccinating in the USA during their official stays.
The reason for this is rather simple: pilots and flight attendants are not allowed to fly for 48 hours after vaccinations. This regulation, which is largely uniform internationally, serves to ensure safety so that you do not get into difficult situations because of side effects. The stays during the so-called stopovers are usually shorter than 48 hours. It could happen that a flight cannot be carried out at all because crew members are not allowed to fly because of the vaccination. Silence would be a serious violation of air traffic control and, in the mildest case, would at least result in a warning.