1. What is this study about?

The Centre for Respiratory Diseases and Meningitis (CRDM) houses the World Health Organization (WHO) National Influenza Centre, which conducts ongoing surveillance for influenza in South Africa. This study describes the results of influenza surveillance, conducted through three respiratory illness surveillance programmes, during 2024. The study describes the epidemiology of the influenza season, antigenic and genomic characterisation of circulating viruses, and influenza vaccine effectiveness for 2024.

2. Why does this matter?

Influenza viruses are continuously evolving, and therefore, the influenza vaccine needs to be regularly updated to ensure it provides protection against circulating viruses. The WHO Global Influenza Surveillance and Response System (GISRS) meets twice per year to decide on the composition of the influenza vaccine. Our data provides important information on influenza epidemiology and virus evolution for South Africa and the Southern Hemisphere.

3. What drew your interest in this area of research?

Influenza causes significant morbidity and mortality each year, and in South Africa we have a large number of people who are considered at high risk for severe influenza disease. Annual influenza vaccination remains the most effective way to prevent severe disease. However, because the influenza virus evolves rapidly through antigenic drift, the flu vaccine is updated every year to make sure it provides the best protection against viruses circulating in the season. Through our surveillance, we ensure that data from South Africa is available for consideration when vaccine composition decisions are made, and therefore flu vaccines can be updated to protect people in South Africa and Africa.

4. What was your role in the study?

CRDM includes a large team at NICD as well as the surveillance sites that collect data and specimens throughout the year for respiratory pathogens of public health importance, which made this study possible. The National Influenza Centre conducts detailed virus characterisation, including both phenotypic antigenic characterisation and genomic characterisation through whole genome sequencing, to understand how influenza viruses are evolving in South Africa and the region.

5. Why should people read this article?

This article describes how the NICD conducts ongoing respiratory illness surveillance to monitor the epidemiology and virus evolution of influenza in South Africa, and shares this data with the WHO to guide decisions on the composition of the influenza vaccine. The article provides information on the influenza season experienced in South Africa in 2024, including dominant subtypes and clades that were circulating, as well as antigenic drift in our setting and resulting influenza vaccine effectiveness.

6. What impact do you hope this surveillance will have on public health policy and access to healthcare?

The data generated in this study was shared with the WHO and included in the GISRS vaccine composition meeting held in September 2024, when the vaccine strains for the 2025 Southern Hemisphere influenza vaccine were decided. We also hope that this study will increase awareness of influenza and encourage influenza vaccination prior to the upcoming 2025 influenza season, especially among high-risk individuals. The surveillance programmes described in this study are also important to monitor for any new and emerging influenza viruses that may have pandemic potential.

Dr Nicole Wolter is a Principal Medical Scientist at the Centre for Respiratory Diseases and Meningitis, National Institute for Communicable Diseases, a division of the National Health Laboratory Service, Johannesburg, South Africa.

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