Can vaping (0 nicotine) still affect sperm?

My husband had been smoking normal cigarettes for around 11 years and about 3 years ago he switched to vaping so to improve his general health.

About a year ago we started TTC to no luck and so we both got tested. His sperm analysis wasn’t the best but it wasn’t the worst in fact the gynae just told me they look normal. Still both his motility and morphology can be better. So about a month ago he dropped his nicotine to 0 so to try to make some improvements.

Will 0 nicotine still have bad effects on sperm? Should he just try and quit?

Thank you all ♥️