SMS messages are crammed into the messages your phone exchanges during ‘pings’ to register with the local cell tower. It literally costs the telco nothing to exchange texts between subscribers on the same network, and as far as I know, telcos don’t charge each other for exchanging SMS messages, because the cost of tracking it all exceeds the practically zero cost of just forwarding the message.
The numbers are still in favour of getting vaccinated. Complications from the vaccine are as close to zero as any medical procedure could be. The complications from raw-dogging COVID are far greater, regardless of your cohort. Turning a life-threatening infection into an inconvenience is what the vaccines do. If your concern is minimizing total risk, getting a COVID booster each year with your flu vaccine is the way to go.