MERS had a much, much higher fatality rate (~35%) and infected a small handful of people (~2500) so it's harder to get meaningful data.
>Two findings emerge: first, the T cells generated back then are still active 17 years on. And second, those old T cells offer protection against the new coronavirus. https://www.telegraph.co.uk/health-fitness/body/no-antibodie...
The first time you face a new virus, you don't have antibodies. You also have no information to generate them. Generating this information takes a long time, which is dangerous.
If you reinfect again after 12 months, you don't have antibodies, but there are cells that contain the information to regenerate the antibodies much faster than the first time you faced the virus.
So reinfection is not as dangerous as the first time.
As a parent of young kids who manages to catch the stomach flu at least once a year from them, this is something I've come to appreciate a ton.
The first time we caught it after neither me nor my wife having caught such a thing for over a decade, it knocked us out for two days. Just completely miserable.
Now, four years and half a dozen rounds later, it's still terrible, but only lasts twelve hours or so.
Gotta love the immune system.
I imagine we're starting to look at people who had severe cases in March, and survived to see if their immune responses are still holding up 3-4ish months after and will be doing so for the months to come.
In a dynamic long-term analysis, such mild reinfections might even be for-the-best: it refreshes your immune response, and those around you in a similar situation, as if the virus itself had been turned into a naturally-circulating seasonal "booster shot".
What if the other four known 'common cold' coronaviruses were all just as challenging as Covid-19 when they emerged... but nowadays, everyone gets them 1st when young – & their immune system most able to adapt – thus rendering them relatively mild, or even undetectable, on all subsequent re-exposures over an entire lifetime?
Pretty sure the same could be said of C19, depending on how you define "most". However, cursory googling shows that there are _1 billion_ cases of common cold in the US alone every year (lots of people have it more than once), so it'd still seem like it'd be worthwhile if it were doable. Common cold accounts for 40% of all time lost from jobs and 30% of lost school time.
I might do that myself, but I’m not sure it would sell well enough to fund the costs of developing the vaccine.
I hate colds, so I might do that, but it would hardly be a best seller.
Couldn't the same be said for the common flu? Most people shrug off influenza, but they develop a new vaccine for that something like twice a year (the efficacy of which isn't great.. https://en.wikipedia.org/wiki/Influenza_vaccine#Effectivenes...)