Except that tweet isn&#x27;t really accurate - vaccine research is pretty active, and modern, new vaccines have made their makers a fair bit of money.<p>Beyond that, vaccines <i>are</i> a &quot;Pay $X per month while healthy&quot; treatment - you have to treat <i>everyone</i> whether they&#x27;re sick or not, and as long as humans keep breeding, you have a replenishing customer base unless we manage the (rare) feat of eradication.<p>The problem is that modern vaccine targets are <i>hard</i>. Multiple strains, dangerous responses from partial immunity (Dengue), very rapid viral evolution (HIV, flu), etc.