It is contagious in the sense that many people exposed to those who have contracted the disease whether in the home or at indoor dining in a restaurant or at indoor family gatherings, have caught Covid-19. But, many in the same circumstances, have not.
Why is it that not everybody who is exposed, contracts the disease, yet others do. Even in NYC with the mass weddings and funerals, only a relatively small percentage seemed to have contracted it. Who knows why? Maybe the exposed but non stricken, have stronger immune systems that warded off the infection. If so, whatever hormones or genetic markers they have, should be found to see if those indicators might have thwarted the infection.
Yes, it would be interesting if a scientific study could establish why this is the case. Again, maybe it is something about body chemistry that confers resistance to those who don't catch it. Even with the highly contagious Spanish Flu , not everybody caught it and those who did, did not always die.
Let's hope answers are found, and in the meantime, that vaccinations will be available to all, very soon.