I agree with being cautious (I started wearing a face mask in mid-March well before anyone was advising this) - but promoting this idea that antibodies don’t give some level of immunity is harmful and anti-scientific. Consider:
1) the human body seems to be able to clear the virus by itself in the vast majority of cases. The only way to do so is via an immune response.
2) if you can’t get immunity via antibodies then why are billions of dollars being spent to develop a vaccine which is designed to initiate the production of such antibodies?
I’m unaware of any studies that have shown that humans do not develop resistance after infection from Covid-19 (and I’ve read a lot of studies).
Yes - we don’t know how long immunity lasts; however, that is due to the short period of time that has elapsed since the emergence of this virus and is not evidence that there is no immunity conferred for some period of time.
Remember, sowing fear, uncertainty and doubt are effective tools for timeshare salespeople, they are also useful tools for public health officials and politicians. That does not mean long-standing scientific knowledge of immune systems should be disregarded.
In the arena of immunology, we should just follow the science. Comments like "I’m unaware of any studies that have shown that humans do not develop resistance after infection from Covid-19" is proof of nothing. I'm unaware of any studies that have shown COVID isn't part of an alien plot from a secret society living on the dark side of the moon. So is that "evidence" that there is, in fact, a secret society on the dark side of the moon using COVID as a plot against us? Of course not.
The LACK of studies doesn't prove anything. It is the OUTCOME of studies that prove things.
So, what you/we are looking for are studies that demonstrate the immunity, and inform us as to it breadth, depth, and longevity. You've read a lot of studies. But you didn't mention that any of THOSE exist yet.
It seems likely that some degree of immunity exists in those that have been infected. But we know nothing more, yet. Does a mild/low viral load infection provide the same degree of immunity as a high viral load, for instance. Do all people develop the same immunity or do some develop a strong lasting immunity and others a very weak immunity? If you are taking an immunosuppresive drug for psoriasis or RA or IBS or a host of other things, does that change whether you are immune? So many unknowns at this early point in time that it is irresponsible to ASSUME you cannot become reinfected now, or 4 months from now, and based on that assumption disregard things like social distancing and face masks. We will know in time, but until we do, it is safer for everyone to act as if you can get reinfected.