Background: Rhode Island (RI) has a universal vaccine policy. Rotavirus (RV) vaccine coverage in RI is estimated to be 84.4% in 2013. The use of a single RV vaccine and RI's high vaccination rate provide an opportunity to study effect of vaccination on circulating RV genotypes. In RI, prior to the introduction of RV vaccine, G1 was the prevalent genotype. From 2006-2009, children received RV5. In 2010, RV1 became the RV vaccine provided.
Methods: Cases were identified using active hospital based surveillance of patients aged <10 admitted to Hasbro Children's Hospital with gastroenteritis from 1/1/02 to 12/31/12. From 2012 to 5/15/2015, cases were identified if a stool sample was sent for RV testing. Stool samples were tested for RV using a commercially available EIA. Viral RNA was extracted and VP7 genotyping was performed using semi-nested Reverse Transcription PCR for primers specific for G1, G2, G3, G4, and G9. Sequencing of nontypeable (NT) strains is ongoing. Vaccination history was reviewed using RI's immunization registry.
Results: Of 841 RV + stools, 762 (91%) were available for genotyping. Of those, 60 (8%) were NT. Implementation of RV vaccine decreased the number of RV admissions/year (Figure 1). G1 was the predominant genotype in all but 1 year prior to RV introduction (Figure 2). G1 remained the predominant genotype following introduction of RV5 in 2006. After the introduction of RV1 in 2010, the predominant genotype was G2 (90%). Thereafter, the predominant type is NT. Of the NT strains sequenced, all (n=9) are G12. RV vaccine coverage of at least 1 dose in cases was 47%. RV5 was administered to 50% of cases (n=9). Of the 2015 cases, RV1 was administered to 83% (n=5).
Conclusion: RV vaccination decreased RV disease in RI. G1 was the prevalent genotype in RI prior to RV vaccine introduction and after implementation of RV5. Variation in genotype distribution occurred only after adoption of RV1. Continued surveillance is needed to determine if the increase in hospitalization in 2015 is related to genotype variation secondary to vaccine induced immune pressure or due to natural variation.
P. H. Dennehy, Merck: Grant Investigator , Research grant