In 2006 a rotavirus (RV) vaccine (Rota Teq®) was licensed for routine childhood immunization in the US. The aim of the present study was to track changes in RV hospital visits and to monitor circulating RV genotypes as vaccination was introduced into New Orleans, Louisiana.
From July 2005 to June 2009, RV-positive stool specimens were systematically collected, viral RNA was extracted and subjected to semi-nested multiplex Reverse-Transcription PCR with primers specific for the gene 9 (G) types G1, G2, G3, G4, G9, and the gene 4 (P) types P, P, P, P and P. Clinical records of RV-positive children were reviewed.
As RV-vaccination was introduced, there was a decrease in the rate of RV-positive cases (per 1,000 hospital visits) from 3.82 to 0.73. A change was noted in the prevailing genotypes, from a predominance of G1P strains to a predominance of G3P. Most affected children were unimmunized. Sequence analysis of gene 9 and gene 4 showed that the circulating strains remained relatively stable over the years studied in this project.
In New Orleans, G3P is becoming a predominant strain of RV. The cause of this change observed has not been determined. It is unclear whether this phenomenon represents natural variation or it is caused by introduction of vaccines.