Universal rotavirus vaccination using RotaTeq® (but not
Rotarix®) vaccine commenced in the state of South Australia in 2008 with a significant reduction in children admitted with disease. However, the vaccine strain is detected by our diagnostic PCR and interferes with the diagnosis of wild type infection. We have evaluated a RotaTeq® specific PCR assay to identify vaccine strains in clinical specimens. Rotavirus genotyping and VP6 sequencing of samples were performed to confirm the presence of vaccine strains. During December to April faecal specimens submitted to SA Pathology and requesting routine enteric viral PCR testing (rotavirus, noroviruses 1 and 2, adenovirus 40/41) were tested in parallel with a VP6 PCR specific for RotaTeq® vaccine strains. A sub sample of rotavirus positive specimens underwent genotyping (VP4 and VP7) and VP6 sequencing.7033 samples from patients were analysed. 223 (3.2%) samples tested positive for rotavirus, of which 65 (24.3%) were RotaTeq® PCR positive. 64 (98.5%) RotaTeq® positive samples came from patients aged between 6 and 30 weeks and one positive sample was from a child aged 94 weeks. In children less than 32 weeks of age, 12.1% of all samples and 71.9% of rotavirus PCR positives samples were RotaTeq® PCR positive. A subset of 121 rotavirus positive faeces (including 46 RotaTeq® RT-PCR positive) were genotyping for VP4 and VP7. The presence of RotaTeq® virus was confirmed by VP6 sequencing in 45/46 (97.8%) of the RotaTeq® RT-PCR positive samples.
RotaTeq® vaccine derived viruses are the most common rotaviruses detectable in children less than 32 weeks of age, but are rarely detected in older children or adults. The use of a PCR screening assay able to discriminate between vaccine and wild type rotaviruses will enable better identification of pathogens in young children and detection of persistence in or spread beyond the target population.