Vaping is worse than smoking weed...
I strongly recommend having a talk about drugs and their addictive potential. I would definitely not ignore the issue, afraid to talk about it, like many parents do. Certainly your kid doesn't want to get involved in something he might regret. Although, kids are usually heavily influenced by their friends, especially at that 14-16 age group. IMO, this is the hardest age group to parent, as they no longer feel the need to respect/fear authority figures yet are still too young to think long-term. Even 11th and 12th graders react better to teachers/coaches/parents because their ability to think long-term and rationally is 100x better than those of that 14-16 age group. My recommendation is to focus on:
A). The impacts of e-cigs. This stuff has been marketed to young people specifically because young people aren't aware of their health risks (unlike regular cigs). They're bad things. If they want to argue with you about your weed, explain that their brains aren't fully developed until 25. Even weed can have a negative impact on their health at this age.
B). The importance of having good friends and high goals. Maybe he has aspirations to obtain a college scholarship through band? Your son doesn't want to put all of that at risk because of friends or drugs. E-cigs are addictive and damaging to the brain development.
https://www.lung.org/stop-smoking/smoking-facts/impact-of-e-cigarettes-on-lung.html
https://www.webmd.com/smoking-cessation/features/vape-debate-electronic-cigarettes#1
C). I'd avoid trying to make him feel guilty or taking away privileges (yet). Again, in my experience, being accusatory and trying to make them feel guilty will backfire. They'll be filled with the attitude of "us (my friends and I) against them (teachers/coaches/religious figures/parents)." Have an open discussion, see what you uncover, and explain your concerns. Ultimately, you want what's best for your son and he should know that through your conversation.
However, he should know that the use of e-cigs as a minor is illegal. Being caught with e-cigs will result in school suspensions. As I remember when I worked in our public education system it resulted in a short suspension and a mandatory drug class for the first offense. The second offense results in a 30+ day suspension. The third offense could potentially lead to expulsion. It is also a misdemeanor in Utah, which could result in him paying fines and losing his employment. Despite your love for your son and your desire for him to invite friends over for fun, you also have every right to protect your home from these types of activities.
https://le.utah.gov/xcode/Title76/Chapter10/76-10-S105.html?v=C76-10-S105_1800010118000101