Trends in Rate of Seizure-Associated Hospitalizations Among Children <5 Years Old Before and After Rotavirus Vaccine Introduction in the United Sates, 2000-2013.

Background: Rotavirus is a common cause of acute gastroenteritis and has also been associated with generalized tonic-clonic afebrile seizures. Since rotavirus vaccine introduction, hospitalizations for treatment of acute gastroenteritis have decreased. We assess whether there has been an associated decrease in seizure-associated hospitalizations. Methods: We used discharge codes to abstract data on seizure hospitalizations among children <5 years old from the State Inpatient Databases of the Healthcare Cost and Utilization Project. We compared seizure hospitalization rates before and after vaccine introduction, using Poisson regression, stratifying by age and by month and year of admission. We performed a time-series analysis with negative binomial models, constructed using prevaccine data from 2000 to 2006 and controlling for admission month and year. Results: We examined 962899 seizure hospitalizations among children <5 years old during 2000-2013. Seizure rates after vaccine introduction were lower than those before vaccine introduction by 1%-8%, and rate ratios decreased over time. Time-series analyses demonstrated a decrease in the number of seizure-coded hospitalizations in 2012 and 2013, with notable decreases in children 12-17 months and 18-23 months. Conclusions: Our analysis provides evidence for a decrease in seizure hospitalizations following rotavirus vaccine introduction in the United States, with the greatest impact in age groups with a high rotavirus-associated disease burden and during rotavirus infection season.

Effect of Age at Vaccination on Rotavirus Vaccine Effectiveness in Bolivian Infants.

BACKGROUND: Rotavirus vaccines are less effective in developing countries versus developed countries. One hypothesis for this difference in performance is that higher levels of maternal antibodies in developing countries may interfere with vaccine response, suggesting that delayed dosing could be beneficial. The present analysis aims to assess whether rotavirus vaccine effectiveness (VE) varies by age at vaccination during routine use in Bolivia. METHODS: Data were merged from 2 postlicensure evaluations of monovalent rotavirus vaccine (RV1) in Bolivia, where 2 doses of RV1 are recommended at 2 and 4 months of age. For each dose, children were classified as receiving each dose "early," "on-time" or "late." Stratified unconditional logistic regression models were used to estimate VE, using unvaccinated children as the referent. VE was calculated as (1 - odds ratio) × 100%. Models were adjusted for hospital, age and time since RV1 introduction (via including terms for month and year of birth). RESULTS: VE for 2 doses of RV1 tended to be higher in infants receiving the first dose early (VE, 92%; 95% confidence interval: 70%-98%), when compared with infants receiving their first dose on-time [72% (62%-81%)] or late [68% (51%-79%)]. Estimates of VE were not substantially different when comparing children by age at second dose [early: VE, 76% (50%-89%); on-time: VE, 70% (50%-89%); late: VE, 75% (60%, 84%)], including all children. CONCLUSIONS: Our results indicate that early administration may improve VE and support the current World Health Organization recommendations for the RV1 schedule.

Sustained Effectiveness of Rotavirus Vaccine Against Very Severe Rotavirus Disease Through the Second Year of Life, Bolivia 2013-2014.

BACKGROUND: In Bolivia, monovalent rotavirus vaccine was introduced in 2008 and a previous evaluation reported a vaccine effectiveness (VE) of 77% with 2 doses of vaccine in children aged <3 years. This evaluation sought to determine if rotavirus vaccine provided protection through the second year of life against circulating genotypes. METHODS: A case-control study was performed in 5 hospitals from April 2013 to March 2014. Among enrolled participants who met study criteria and had rotavirus stool testing performed and vaccine status confirmed, we calculated VE using a logistic regression model. Subgroup analyses were performed among children aged <1 year and those aged ≥1 year, among children with severe diarrhea (Vesikari score ≥11) and very severe diarrhea (Vesikari score ≥15), and among G and P strains with at least 40 specimens. RESULTS: A total of 776 children were enrolled. For children <1 year and ≥1 year of age with severe diarrhea, VE for 2 doses was 75% (95% confidence interval [CI], 46%-88%) and 53% (95% CI, 9%-76%), respectively. For children <1 year and ≥1 year of age with very severe diarrhea, VE for 2 doses was 80% (95% CI, 44%-93%) and 74% (95% CI, 35%-90%), respectively. Genotype-specific analysis demonstrated similar VE for the 4 most common G and P types (G3, G9, P[6] and P[8]). CONCLUSIONS: A monovalent rotavirus vaccine remains effective against a broad range of circulating strains as part of a routine immunization program >5 years after its introduction in Bolivia. Although VE appears to wane in children aged ≥1 year, it still provides significant protection, and does not wane against severe disease.