Smoking's harms are observable in the short term! You don't need long-term longitudinal studies to show smoking is bad. And we have known mechanisms for that harm that relate to combustion. We know mechanically that vapes are not combusting plant material, and we also don't see the same kinds of obvious harms in the short term. It takes willful blindness to the ills of smoking to suggest that vaping might be as harmful or more harmful than smoking.