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Published on: January 28, 2019
Impact of rotavirus vaccination in Malawi from 2012 to 2022 compared to model predictions
Virginia E Pitzer1,2,3, Latif Ndeketa4,5, Ernest O Asare6,7
1Department of Epidemiology of Microbial Disease, Yale School of Public Health, Yale University, New Haven, CT, USA. virginia.pitzer@yale.edu.
Insights
The Rotarix® vaccine introduction in Malawi showed a substantial decline in rotavirus gastroenteritis cases. Overall vaccine effectiveness was modest at 36%, highest in infants, highlighting its public health impact.
Area of Science:
- Pediatrics
- Vaccinology
- Public Health
Background:
- Rotavirus gastroenteritis (RVGE) is a leading cause of severe diarrhea in children globally.
- Malawi introduced the Rotarix® vaccine into its national immunization program in October 2012.
- Assessing vaccine effectiveness and impact is crucial for public health strategies in low-income settings.
Purpose of the Study:
- To analyze the impact of Rotarix® vaccine introduction on RVGE hospitalizations in children under 5 years old in Malawi.
- To estimate rotavirus vaccine effectiveness (VE) using a mathematical modeling approach.
- To evaluate vaccine coverage trends, including during the COVID-19 pandemic.
Main Methods:
- Retrospective analysis of hospitalization data for acute gastroenteritis from January 2012 to June 2022, compared to pre-vaccination data (1997-2009).
- Estimation of vaccine coverage using rotavirus-negative children as controls.
- Comparison of observed RVGE cases with model-predicted incidence to estimate overall VE and age-specific effectiveness.
Main Results:
- A substantial decline in RVGE and rotavirus-negative acute gastroenteritis cases was observed post-vaccine introduction.
- Vaccine coverage exceeded 90% by July 2014, dipped to ~80% in October 2020, and recovered by July 2021.
- Overall VE was estimated at 36.0% (95% PI: 33.6%, 39.9%), with highest effectiveness in infants (52.5%; 95% PI: 50.1%, 54.9%).
Conclusions:
- The Rotarix® vaccine has had a significant impact on reducing RVGE hospitalizations in Malawi.
- Mathematical models provide a validated tool for assessing rotavirus vaccine impact in resource-limited settings.
- Strategies to improve vaccine impact, particularly in older age groups, may be warranted.
Abstract:
Rotarix® vaccine was introduced into the Malawi national immunization program in October 2012. We analyzed data on children <5 years old hospitalized with acute gastroenteritis from January 2012 to June 2022, and compared to pre-vaccination data from 1997 to 2009. We estimated vaccine coverage before, during, and after the COVID-19 pandemic using data from rotavirus-negative children. We compared the observed weekly number of rotavirus-associated gastroenteritis (RVGE) cases by age to predictions from a previously developed mathematical model to estimate overall vaccine effectiveness. The number of RVGE and rotavirus-negative acute gastroenteritis cases declined substantially following vaccine introduction. Vaccine coverage among rotavirus-negative controls was >90% with two doses by July 2014, and declined to a low of ~80% in October 2020 before returning to pre-pandemic levels by July 2021. Our models captured the post-vaccination trends in RVGE incidence. Comparing observed RVGE cases to the model-predicted incidence without vaccination, overall effectiveness was estimated to be modest at 36.0% (95% prediction interval: 33.6%, 39.9%), peaking in 2014, and was highest in infants (52.5%; 95% prediction interval: 50.1%, 54.9%). Our mathematical models provide a validated platform for assessing strategies to improve rotavirus vaccine impact in low-income settings.
