Quantifying the Impact of Switching From Rotarix to Rotavac Rotavirus Vaccine in Ghana

BACKGROUND: Ghana introduced the Rotarix vaccine in April 2012 and switched to the Rotavac vaccine in January 2020. Evaluating the health impact of this change is essential for national policy and can inform decisions in other countries. METHODS: We applied a previously validated mathematical model of rotavirus transmission in Navrongo, Ghana, to quantify the health impact of switching from Rotarix to Rotavac among children under 2. We first simulated the model from January 2007 to December 2019 using previously estimated model parameters from pre- and post-Rotarix surveillance data. We then refitted the model to data from January 2020 to March 2023 to estimate Rotavac vaccine effectiveness parameters. To assess overall vaccine effectiveness (OVE), we compared model simulations under the 2 vaccination scenarios (Rotarix and Rotavac) with a counterfactual scenario assuming no vaccination. RESULTS: The model accurately captured both the trend and seasonality of postvaccination rotavirus cases, with a Spearman correlation of 0.70. Compared to the no-vaccination scenario, the estimated OVE against moderate-to-severe rotavirus cases was 21.7% (95% prediction interval [PI]: 17.4%-26.1%) in children under 2 years in Navrongo. Annual OVE ranged from 8.4% (PI: 1.0%-21.0%) to 63.5% (PI: 39.0%-87.0%). Following the switch from Rotarix to Rotavac (2020-2023), we estimated a mean relative OVE of 37.1% (PI: 27.5%-46.5%). CONCLUSIONS: Our model offers a robust tool to support policymakers in Ghana and similar settings by evaluating current rotavirus vaccine effectiveness, guiding vaccine switching decisions and informing introduction strategies in countries yet to adopt immunization.