I caught the flu in Melbourne at a Uni conference 40 years ago and have never forgotten how ill I was. When work started offering flu injections as part of OH&S I jumped at it and have had them for many years without ill effects beyond an occasional warm arm at the injection site. My husband also has had flu injections for years at work and now in retirement at home .
My children have have been having them too as they are attending high school and many bugs circulate in that environment. In addition two of my kids have had asthma .We thought it wise for our health as ageing parents too that they be inoculated especially so since my cancer diagnosis .None have had side effects beyond what I described.
My only negative is one year ( last ?) my sons both got flu despite being inoculated as the strain circulating was not in the vaccine.Luckily they are very fit and healthy but both were laid low for a week.
I would never travel o/s without a flu injection nor even a lengthy flight domestically in flu season.It seems almost inevitable to pick up a cold on a flight but the flu I’d prefer to avoid.
It’s not an ironclad guarantee but it provides protection against major strains circulating and imo is very worthwhile.