I had the same initial reaction and did some googling to see if it was a term of art, but couldn't find anything to support my hypothesis. I am interpreting "r

I had the same initial reaction and did some googling to see if it was a term of art, but couldn't find anything to support my hypothesis. I am interpreting "relevance" here as meaning that it's a factor in the epidemic. Increased relevance means vaccinated people are increasingly a factor in (i.e., contributing to) the spread of COVID-19.