This is a metareview, that is a summary of actual research papers, regarding household transmission. (Medrxiv Paper) 40 studies were included. An overall secondary attack rate (one person in a household affecting another) was put at 19%. Symptomatic persons were much more likely than asymptomatic ones to be the index case (the infector), in fact more than 20 times more likely. Adults were more likely to be the infectee than children, and households of two much more likely to have a secondary infection than those with three or more people. One explanation for the latter finding may be that larger households have more children and may have more shared prior coronavirus infections which build immune response.
This study is another one looking at antibody persistence. (Medrxiv Paper) The authors compared antibody levels in health care workers with non-severe CV infection with those in hospitalized patients. They found antibody levels correlated with disease severity. The found that spike and receptor binding domain antibodies waned in the health care workers but not nucleocapsid antibodies. They cautioned that the results might led to accuracy issues with infection prevalence testing. Note also that even nucleocapsid antibodies could be neutralizing and could be part of a robust immune response to reinfection.
In this paper, the researchers looked at cross-reactivity of antibodies from the original SARS strain to this one. They found very strong cross-reactivity across several antibodies. This could suggest that a vaccine might be protective against multiple SARS variations. (Medrxiv Paper)
To help elucidate disease processes, these authors examined the interaction of the spike protein of CV with the innate immune system. (Medrxiv Paper) The innate immune system is what helps fight off first-time acute infections. The spike region is significantly coated with chemicals called glycophosphates, which tend to be recognized and engaged by many innate immune cells. This means that the virus may be able to infect some of these cells, which are supposed to be protecting us, and can prompt an excessive immune response which causes an exacerbation of illness.