Como dice el artículo de CNN, ha pasado antes.
"There are some viruses that we still do not have vaccines against," says Dr. David Nabarro, a professor of global health at Imperial College London, who also serves as a special envoy to the World Health Organization on Covid-19. "We can't make an absolute assumption that a vaccine will appear at all, or if it does appear, whether it will pass all the tests of efficacy and safety.
Como por ejemplo, el VIH o el Ébola.
He empezado a llamar al covid-19 como Ébola Jr.
Links: We May Never Get a COVID-19 Vaccine | What happens if a coronavirus vaccine is never developed? It has happened before