in those workers whom it was possible to contact for the second phase of the study, the response rate was high (,80%); similarly, the response rate was high for the nonsymptomatic workers whom it was possible to contact for the phase II study
in those workers whom it was possible to contact for thesecond phase of the study, the response rate was high (,80%);similarly, the response rate was high for the nonsymptomaticworkers whom it was possible to contact for the phase II study