vaccine efficacy ranged from a low of 9.6% for infection confirmed by laboratory measure only to 58.7% for infection confirmed both by laboratory measure and by the presence of at least one RSV symptom of grade ≥2, and the differences in infection incidence between the treatment groups were not statistically significant. When infection was defined instead by quantifiable qRT-PCR viral load, efficacy ranged from 51.8% to 79.3%, and differences in symptomatic infection were statistically significant. Finally, when defined by virus culture results alone, vaccine efficacy was 88.5% (p=0.0125); addition of clinical symptoms to the definition did not improve efficacy.
There was a larger phase 2 w 400+ patients but I couldn't find any data. however the results of this call it phase 2b trial did get them BTD and Prime, so I am assuming the data was relatively strong