Seasonal human #coronavirus antibodies are boosted upon #SARS-CoV-2 infection but not associated with protection - ScienceDirect
Does Prior Exposure to Coronaviruses Protect You? | In the Pipeline
... 20% of the[...] patients [previously infected with one or more of the “garden-variety” coronaviruses] raised antibodies that do cross-reaction with the Spike or nucleocapsid proteins of the current pandemic coronavirus. And what’s more, levels of such antibodies are elevated when a person in this group gets infected with SARS-Cov2: the immune system memory (as present in these patients’ B cells) responds by increasing production of the antibodies to the previous coronaviruses.
But here’s the key part: “cross-react” does not mean “neutralize” and it does not mean “provide protection from”. These antibodies may or may not have been neutralizing against the other coronaviruses, but they don’t seem to have any such effect on the current one. And in keeping with that, having such cross-reactive antibodies seems to provide no protection against catching SARS-Cov2 or against being hospitalized with it if you do. There’s no difference in the infection/hospitalization rates of the people who had cross-reactive coronavirus serum antibodies ready to go versus those who didn’t. They’re basically useless.
Now, you can still make an argument that the T cell component of immunity might provide some protection after a previous coronavirus infection. The current study didn’t address this directly, but after these results, it’s at least less likely that that’s happening.