Not that I WANT to get into this part of the debate, but there is very good evidence to suggest natural immunity is better than a created vaccination. Between 7 and 9 times more effective.
So, with a fair few players not wanting a vaccine, it looks like they'd rather get Covid and let their body fight it off, over chemicals in their bodies. But, this are athletes.
You would have to ask if Southgate has demanded a 'jab or don't play' policy (I don't know as I haven't followed national football in years) with an eye on that scuppering progress under his tenure.