Figure 4.

Peak vaccine titers do not appear to be predictive of vaccine efficacy. Peak log₁₀ titers of vaccine virus shed among vaccinees who experienced respiratory syncytial virus (RSV)-associated medically attended acute respiratory illness (MAARI) (blue dots), vaccinees who did not experience RSV-MAARI but had serologic evidence of wild-type (wt) RSV exposure during the RSV season (orange dots), and vaccinees who did not experience RSV-MAARI and who also had no evidence of wt RSV exposure (black dots) during the subsequent RSV surveillance season. Means were calculated for RSV-MAARI+ (blue dots) and for RSV-MAARI− who had evidence of exposure to RSV during surveillance (orange dots). A shows all vaccinees and B shows recipients of the more promising vaccines.