We conducted a phase I clinical trial (clinicaltrials.gov identifier, NCT00641017) of the experimental live-attenuated human parainfluenza virus type 1 (HPIV-1) vaccine rHPIV-1/84/del 170/942A sequentially in 3 groups: adults, HPIV-1-seropositive children, and HPIV-1-seronegative children, the target population for vaccination. rHPIV-1/84/del 170/942A was appropriately restricted in replication in adults and HPIV-1-seropositive children but was overattenuated (ie, insufficiently infectious and immunogenic) for HPIV-1-seronegative children.
Keywords: HPIV-1 vaccine; children; lower respiratory tract illness.
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