The epidemiology of all-cause and rotavirus acute gastroenteritis and the characteristics of rotavirus circulating strains before and after rotavirus vaccine introduction in Yemen: analysis of hospital-based surveillance data.

BACKGROUND

Rotavirus (RV) vaccine was added to Yemen's childhood vaccination schedule in late 2012. We evaluated the effect of vaccination on the epidemiology of acute gastroenteritis (AGE) and the characteristics of circulating RV strains.

METHODS

Surveillance data was obtained at two sentinel hospitals from 5,691 children with acute gastroenteritis (AGE) who were under 5 years of age. Data collected before (2007-2011) and after (2013-2014) RV vaccine introduction were retrospectively analyzed. Treatment outcome, presence of severe dehydration, and the proportion of all-cause AGE due to RV-antigen positive AGE were calculated for each period and compared. Binominal generalized linear models were used to calculate adjusted odds ratios (ORs) and 95 % confidence intervals (CIs). We also compared severe RVAGE and severe dehydration proportions in hospitalized children with severe AGE and characterized RV circulating strains in available specimens from the two periods.

RESULTS

Before RV vaccination, mean RVAGE prevalence peaked in October (58.8 %), November (69.5 %), and December (56.4 %). In 2013-2014, the variation became less defined, with only a few RVAGE cases. The average annual prevalence of severe RVAGE needing hospitalization was 42.9 % in 2007-2011, decreased to 21.1 % in 2013, and to 18.5 % in 2014, representing declines of 50.8 % (95 % CI: 36.4-65.0) and 56.9 % (95 % CI: 42.1-70.5). The proportion of children <12 months of age with all-cause AGE decreased significantly after introduction of RV vaccination (58.7 % vs. 62.3 %; p = 0.042), severe dehydration decreased by 50 % (14.7 % vs. 21.7 %; OR = 0.501, p < 0.0001), and RVAGE proportion decreased by 48 % (19.9 % vs. 41.6 %; OR = 0.52, p < 0.0001). The proportion of severe RVAGE in hospitalized patients decreased by 67 % (20.1 % vs. 43.5 %; OR = 0.33, p < 0.0001), and severe dehydration decreased by 58 % (17.2 % vs. 33.1 %; OR = 0.42, p < 0.0001). Non-RV AGE prevalence significantly increased, with ORs of 2.8-3.1 in favor of non-RV AGE in 2013-2014. Analysis of 128 available stool specimens revealed that circulation of the G1 genotype did not change following vaccination (33.3 % vs. 41.3 %; p = 0.366). G2 significantly decreased in 2013-2014 (4.2 % vs. 42.5 % p = 0.0001), and G9 increased (29.2 % vs. 6.3 %; p = 0.001). G1P[8] and G2P[4] remained prevalent, and G9P[8] and G9P[4], which were not detected in the pre-vaccine period appeared in 2013-2014. G and [P] mixed genotypes became more prevalent in 2013-2014. It is not known if this predominance is related to the vaccine introduction or attributable to normal genotype fluctuations.

CONCLUSIONS

Rotarix substantially reduced the prevalence of RVAGE, with a 67 % reduction of severe RVAGE hospitalizations, and over 50 % reduction of diarrhea with severe dehydration. Circulation of RV G and [P] mix strains was significantly increased in 2013-2014 and needs continuous monitoring.