Moderna stated that the antibody levels seen were on a par with — or greater than, in the case of the 100-microgram dose — those seen in people who have recovered from Covid-19 infection.

.... studies have shown antibody levels among people who have recovered from the illness vary enormously; the range that may be influenced by the severity of a person’s disease. John “Jack” Rose, a vaccine researcher from Yale University, pointed STAT to a study from China that showed that, among 175 recovered Covid-19 patients studied, 10 had no detectable neutralizing antibodies. Recovered patients at the other end of the spectrum had really high antibody levels.

So though the company said the antibody levels induced by vaccine were as good as those generated by infection, there’s no real way to know what that comparison means.....

....the exact ages of these eight people (with response) are unknown. If, by chance, they mostly clustered around the younger end of the age spectrum, you might expect a better response to the vaccine than if they were mostly from the senior end of it. And given who is at highest risk from the SARS-CoV-2 coronavirus, protecting older adults is what Covid-19 vaccines need to do.