Impact of rotavirus vaccination in Malawi from 2012 to 2022 compared to model predictions.

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.
Competing Interests: Competing interests D.H. is currently receiving grant support from Seqirus UK Ltd for the evaluation of influenza vaccines and grant support and personal consultancy fees from Merck & Co (Kenilworth, New Jersey, USA) for rotavirus strain surveillance; D.H. received honoraria for a presentation at a Merck Sharp & Dohme (UK) Limited symposium on vaccines; and D.H. has previously received research-initiated and industry-initiated research grant support from GlaxoSmithKline Biologicals for evaluation of rotavirus vaccination in the UK and from GSK, Sanofi Pasteur, and Merck & Co for rotavirus strain surveillance. BAL reports personal fees from Epidemiological Research and Methods, LLC. MO and reports receiving grants and research support from Janssen Vaccines & Prevention B.V., Bharat Biotech International Limited, and HilleVax Inc. outside of the submitted work. K.C.J. has received research grant support from GlaxoSmithKline Biologicals for work on rotavirus vaccines. All other authors declare no competing interests.
(© 2024. The Author(s).)