Investigations of clinical isolations of oral poliovirus vaccine strains between 2000 and 2005 in southern Taiwan

Abstract

Background In Taiwan, trivalent oral poliovirus vaccine (tOPV) is in the routine immunization schedule, but its association with illnesses had not been examined. Objectives To investigate clinical presentations and viral characteristics of patients with poliovirus isolates. Study design Clinical data, vaccination records and viral sequences were retrospectively analyzed for patients from whom polioviruses were isolated during 2000–2005. Results OPV-like strains were the only pathogen identified in 208 children who were diagnosed with lower respiratory tract infection (24.5%), acute gastroenteritis (16.8%) or upper respiratory tract infection (10.6%). Timing of poliovirus isolation relative to the tOPV vaccination was unusual in 59 patients, including 6 before any dose and 53 more than 10 weeks after the 3rd or later dose of tOPV. Sequence analyses of the VP1, 2C and 3C/D regions for 19 poliovirus isolates revealed that 4 had previously reported neurovirulence reversions, 1 had intertypic recombination, and 6 had both. No patient had neurological complications, but 3 died of myocarditis, including 2 with recombinant strains and 1 who never received OPV. Conclusion This study describes the isolation of OPV-like strains from patients with a variety of illnesses, raising concerns about their pathogenic potential in an area where tOPV is routinely administered. The detection of genetic variations among OPV-like strains warrants continuing surveillance for these variants in patients with severe illnesses besides neurological complications.