during 20082010 , fecal samples were collected from 3,852 children ; 702 specimens ( 18.2% ) had rva - positive elisa results ; 27 of those ( 3.8% ) were characterized as g1p by using reverse transcription - pcr . * prefixes represent origins of circulating strains in brazil : es , espirito santo ;  , no data ; se , sergipe ; pe , pernambuco ; ma , maranho ; ba , bahia .  age of child at time of fecal sample collection . sequences were compared with those in strains obtained from genbank ( including rotarix jx943604.2jx943614.2 ) . strains analyzed belonged to the wa - like genogroup ( genotype 1 ) ; 26 strains showed a g1p one sample , collected from a child vaccinated with 1 dose during 2010 in maranho ( ma ) state ( ma1903010 ) , contained the g1p  ix nucleotide ( nt ) identity values between circulating strains in brazil and the rotarix strain ranged 76%100% ( table 2 ) . the se1590108 strain , collected on day 7 after the first dose , showed 100% nt identity with all rotarix strain gene segments and could represent vaccine shedding . vaccine antigen excretion detected by elisa achieved 80% , declining to 18%24% when collected at day 30 ; 11%16% of children shed the virus at day 45 ( 6 ) . shedding is not associated with increased gastroenteritis - like symptoms . widespread use of rotarix might reveal adverse reactions not observed in clinical trials , emphasizing the need for global surveillance ( 7 ) . * wa - like , ds-1-like , au - like genotypes are shown in green , red , and orange , respectively , and the p genotype is shown in blue ; x , indeterminate genotypes ;  , no data . one sample for each group was chosen as representative and the average was shown . prefixes represent origins of circulating strains in brazil : se , sergipe ; ba , bahia ; ma , maranho ; es , espirito santo ; pe , pernambuco . in phylogenetic analysis of 11 genes , 10 genes clustered into 5 clades . in the remaining gene , nsp5 , the circulating strains clustered into 4 groups ( figure 1 , panel e ) . phylogenetic analysis of nucleotide sequence of a ) nonstructural protein 1 [ nsp1 ] , b ) nsp2 , c ) , nsp3 , d ) nsp4 , and e ) nsp5 encoding genes of g1p rva samples collected in brazil and described in this study . bootstrap values > 70% , estimated with 2,000 pseudoreplicate datasets , are indicated at each node . only the genotype in which the strains under investigation cluster is shown completely ; 1 prototype from another genotype has been added as an outgroup . strain es1522108 , detected in an unvaccinated child , is genetically distinct and differs in origin from other g1p circulating strains ( figures 1,2 ) . the vp1 gene ( 648 bp , figure 2 , panel a ) in this sample showed 100% nt identity with the rotarix strain . strain ma1900610 was genetically similar to the strain ; however , the nsp5 segment ( figure 1 , panel e ) was closely related to a g1p strain from australia ( jf490152 ) . phylogenetic analysis of nucleotide sequence of ( a ) vp1 , ( b ) vp2 , ( c ) , vp3 , ( d ) vp4 , ( e ) vp6 and ( f ) vp7 genes of g1p rva samples collected in brazil and described in this study . filled circles indicate samples from non - vaccinated children and filled triangles vaccinated children . the rotarix vaccine strain is indicated by a filled diamond . bootstrap values above 70% , estimated with 2,000 pseudoreplicate datasets , are indicated at each node . only the genotype in which the strains under investigation cluster is shown completely and one prototype from another genotype has been added as outgroup . strain ma1903010 , detected in a child after 1 vaccine dose , was closely related to the ma group , but the nsp2 segment differed in origin from other ma samples ( figure 1 , panel b ) because it clustered with other wa - like strains . the nsp3 gene belonged to genotype 3 because it was 99.2% ( nt ) similar to the au-1 prototype strain ( dq490535.1 ) . these results suggested reassortment events between wa - like and au-1 like co  circulating strains . nsp2 and nsp3 genes from sample ma1903010 and nsp5 genes from sample ma1900610 differed from each other and from those of their respective clusters . samples ma1900610 and ma1903010 are genetically distinct and might have distinct evolutionary histories . studies that included this genogrouping system were performed to prove the existence of inter - genogroup reassortment between human rva genogroups or human and animal genogroups . the existence and effectiveness of heterogeneous genome constellations remains unclear , probably because it is caused by mechanisms that create protein sets that work better when kept together ( 8) . phylogenetic analysis of the vp8 * ( aa 1247 ) portion of vp4 encoding gene showed circulating strains ( figure 2 , panel d ) clustered into 2 lineages ( p-3 and p-1 ) . the alignment of the deduced aa sequences showed potential trypsin cleavage sites at arginine 240 and 246 conserved in all samples . all circulating strains contained 91.3%100% identical aa residues to the rotarix strain in vp8 * antigenic epitopes ; no changes were observed on epitopes 82 and 84 . samples closely related to the rotarix strain belonged to g1-ii ; remaining strains belonged to g1-i . comparing the regions defined as antigenic epitopes ( 71 and 72 ) for vp7 protein , we found > 2 epitopes ( aa 94 , 123 , 148 , 217 ) were not conserved among circulating strains compared with the rotarix strain . the following amino acids were conserved in the non - vp7/non - vp4 segments of either the rotarix strain or other strains analyzed : cysteine residues involved in disulfide bonds at positions 6 , 8 , 85 , and 285 in nsp2 protein ; the leucine , isoleucine , aspartic acid , methionine and glutamine at positions 275 , 281 , 288 , and 295 in the nsp3 protein ; the n - linked glycosylation sites at positions 8 and 18 , and cysteine residues at positions 63 and 71 in nsp4 protein ; and serine residues at positions 153 , 155 , 163 , and 165 in nsp5 protein . three strains circulating in brazil were closely related to those in rotarix ; 1 of the 3 was 100% identical to rotarix , likely representing shedding of this vaccine . sequence analysis confirmed the presence of the rotarix vp1derived segment in 1 sample ( es1522108 ) , indicating an unreported reassortment event between the vaccine and a community strain . the backbone of ma1903010 sample was wa - like , but the nsp3 segment exhibited a t3 genotype that was described for the au-1 genogroup . this finding suggests that this strain derived its nsp3 gene from an au-1-like strain through reassortment . changes in antigenic regions of vp4 and vp7 proteins have been associated with mutated rva strains that spread ( 9,10 ) . comparison of the aa sequences of vp7 and vp8 * of strains circulating in brazil and the monovalent vaccine strain demonstrated that vp7 and vp8 * of the circulating strains showed similar antigenic regions to those of the vaccine . considering the segmented rva genome and that the rotarix vaccine is an attenuated rva human strain , it is expected that reassortants will arise and circulate among humans . this study described strains that originated from reassortment events between the rotarix vaccine strain and strains detected in vaccinated and unvaccinated children . improvement of rva surveillance programs that include full genome sequencing analysis will strengthen the understanding of how vaccines will affect the rvas circulating among humans , and how those events could affect the use of live vaccines , the frequency of rva intra- and intergenogroup reassortment events under natural conditions , and the stability of rva generated by such events .
analysis of 27 rotavirus strains from vaccinated and unvaccinated children revealed reassortment events in 3 strains : a gene derived from a vaccine ; a gene acquired from a circulating strain ; and reassortment between circulating strains . 
 data suggest that the widespread use of this monovalent rotavirus vaccine may introduce vaccine genes into circulating human rotaviruses or vice versa .