Did you ever wonder: Hey, the original SARS outbreak was 15 years ago, why don’t we just use the SARS vaccine we put our (and every opportunistic scientist's) all into developing on COVID-19? Oh right, there IS no SARS vaccine. Hmmm. Why is that, exactly?
Well, it turns out vaccines for coronaviruses and some other viruses are not as easy as they look. Alarmingly, there is some evidence that vaccines for some viruses might actually cause worse disease when you encounter the virus and even lead to death, rather than a mild illness. Respiratory syncytial virus is the poster child for this phenomenon: The vaccine produced antibodies that caused an overexuberant immune reaction upon virus exposure that killed some vaccinees. Unfortunately, similar effects were seen in animals during SARS vaccine development and is already suspected for COVID-19. Basically, instead of blocking or clearing the virus, some antibodies elicited by the vaccine trigger an explosive, life-threatening immune response. It is unclear at this point if the antibodies elicited by the current vaccines in testing exhibit more or fewer of these dangerous forms.
While this could pose quite a dilemma for each of us in deciding whether to get a COVID-19 vaccination when one becomes available, any sign of this phenomenon may be pure gold for the so-called anti-vaxxers, who oppose all vaccines and vaccination on conspiratorial grounds. Almost all vaccines have rare risks, but their benefit to population health is enormous and undeniable. Nevertheless, if a not-so-rare risk pops up from a vaccine that was rushed through to market in desperation, cooler minds may not prevail in the subsequent anti-vax onslaught. Sometimes it's better to be the turtle than the hare.