https://www.nejm.org/doi/full/10.1056/NEJMc2032195 https://www.nejm.org/doi/full/10.1056/NEJMc2032195 Shows a slow decay in neutralizing antibody titers in tho

https://www.nejm.org/doi/full/10.1056/NEJMc2032195 https://www.nejm.org/doi/full/10.1056/NEJMc2032195 Shows a slow decay in neutralizing antibody titers in those vaccinated, with a greater degree of viral inhibition months later than convalescent plasma at a month. "At day 119, the binding and neutralizing GMTs exceeded the median GMTs in a panel of 41 controls who were convalescing from Covid-19, with a median of 34 days since diagnosis (range, 23 to 54)." There's also data showing much higher neutralization titers against variants in those vaccinated vs. those naturally infected. Of course, this is only one measure of immune response. Many other things are more difficult to measure, so we don't know too much about e.g. T cell responses from natural infection vs. vaccination. So it's hardly proven but there is some highly suggestive evidence.