In 2006, when RotaTeq, the second oral live rotavirus vaccine received approval for use in the United States, the most common rotavirus serotypes were P1A[8]G1, P1B[4] G2, P1A[8] G3, P1A[8] G4, P1A[8] G9,and P2A[6] G9. It was reported that in infants between three and 35 months of age, the first rotavirus infection would likely be the most severe and 40 percent of children would not have any further rotavirus infections. Seventy-five percent of children would be protected against subsequent rotavirus gastroenteritis, and 88 percent would be protected against subsequent severe rotavirus gastroenteritis. The initial first natural infection was reported to protect an infant against severe rotavirus gastroenteritis in the future but that asymptomatic or mild infections might still occur.
These same six distinct rotavirus serotypes were also noted to be the predominant circulating strains in the United States when ROTARIX, the third oral live rotavirus vaccine was recommended for use by ACIP in 2008.
Surveillance of rotavirus serotypes in the United States following the introduction of RotaTeq found that G3 replaced G1 as the strain most frequently detected and that additional uncommon serotypes had also been detected. Additionally, by the 2007-2008 season, the mean age of rotavirus cases in children less than 3 years had increased significantly. The authors concluded that These findings underscore the need for careful monitoring of strains to assess possible vaccine pressure-induced changes and vaccine effectiveness against various rotavirus genotypes
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G12 rotaviruses were first detected in the Philippines in 1987 among children under the age of two, but then not detected again until 1998. However, since 1998, G12 rotavirus strains have been detected globally. One of the first outbreaks of G12 rotavirus in the U.S. occurred in Rochester, New York in 2006-2007 and this strain contributed to a 72 percent increase in the number of rotavirus cases. Since this first large outbreak, G12 strains have continued to be detected in the U.S. and abroad.
