What he is saying is not true. The large vaccine trials have always been about testing the effectiveness at combating disease directly (measuring rates of repor

What he is saying is not true. The large vaccine trials have always been about testing the effectiveness at combating disease directly (measuring rates of reported illness or hospitalization), with antibody titers used as a quick secondary check. His comment assumes the reverse happened. We still know surprisingly little about how long antibodies are measurable in the blood and for how long and how effective they are at what prevalence rate, etc.