I, too, have had my 5th jab - Moderna.
I've been offered the flu jab, but have declined. I've only ever had flu once, and never had a flu jab. The last time I had a cold was back in 2013 as I arrived in South Africa for a holiday. My friend took me to the local pharmacy and after discussions on my medication, echinacea was recommended. The cold disappeared in less than 2 days, and ever since then I have taken echinacea regularly during the winter months. It works for me, but has no effect at all on OH - but then everyone is different.