Long-term impact of rotavirus vaccination on all-cause and rotavirus-specific gastroenteritis and strain distribution in Central Kenya: An 11-year interrupted time-series analysis

Background: Kenya introduced a monovalent rotavirus vaccine administered orally at 6 and 10 weeks of age into her National Immunization Program in July 2014. The study evaluated the long-term impact of the vaccine on hospitalization for all-cause and rotavirus-specific acute gastroenteritis (AGE) and strain epidemiology in Kenya. Methods: Data on all-cause and rotavirus-specific AGE and strain distribution were derived from an eleven-year hospital-based surveillance of AGE among children aged <5 years at Kiambu County Teaching and Referral Hospital (KCTRH) in Central Kenya between 2009 and 2020. Fecal samples were screened for group A rotavirus using ELISA and genotyped using multiplex semi-nested RT-PCR. Trends in all-cause and rotavirus-related AGE and strain distribution were compared between the pre-vaccine (July 2009–June 2014), early post-vaccine (July 2014–June 2016) and late post-vaccine (February 2019–October 2020) periods. Results: Rotavirus-specific AGE was detected at 27.5% (429/1546, 95% CI: 25.5–30.1%) in the pre-vaccine period; 13.8% (91/658, 95% CI: 11.3–16.6%) in the early post-vaccine period (July 2014–June 2016); and 12.0% (229/1916, 95% CI: 10.6–13.5%) in the late post-vaccine period (February 2019–October 2020). This amounted to a decline of 49.8% (95% CI: 34.6%–63.7%) in rotavirus-specific AGE in the early post-vaccine period and 53.4% (95% CI: 41.5–70.3%) in the late post-vaccine period when compared to the pre-vaccine period. All-cause AGE hospitalizations declined by 40.2% (95% CI: 30.8%–50.2%) and 75.3% (95% CI: 65.9–83.1%) in the early post-vaccine and late post-vaccine periods, respectively, when compared to the pre-vaccine period. G3P [8] was the predominant strain in the late post-vaccine period, replacing G1P[8] which had predominated in the pre-vaccine and early post-vaccine periods. Additionally, we detected considerable proportions of uncommon strains G3P[6] (4.8%) and G12P[6] (3.5%) in the post-vaccine era. Conclusion: Rotavirus vaccination has resulted in a significant ...