Jeffrey Weiser M.D. is a physician-scientist and the C.V. Starr Professor of Microbiology at New York University. He served as chair of this department from 2015-24. From 1994-2014, Jeff was a faculty member in Pediatrics and Microbiology at Children’s Hospital of Philadelphia and the University of Pennsylvania. There he was a colleague of Robert Austrian M.D., who was instrumental in the development of Jeff’s research program on pneumococcal biology. Together they described reversible, intrastrain phenotypic differences in pneumococci referred to as phase variation.

Subsequently, Jeff’s laboratory has investigated multiple aspects of pneumococcal pathogenesis, particularly those related to colonization and host-to-host transmission. Many of these microbiological and immunological studies utilize mouse models, including in infant mice, developed in his laboratory. A particular topic has been the mechanisms responsible for clinically relevant interactions in the upper respiratory tract such as between S. pneumoniae and influenza virus and intra- and inter-species competition among pneumococci.  Research on polymicrobial interactions, for example, shows how successful microbes induce an inflammatory response to which they are resistant, thus prevailing over sensitive competitors. This paradigm, termed ‘within-host-competition’, reveals how competitive interactions account for characteristics enhancing virulence (triggering and resisting inflammatory responses) even though these may harm the microbe’s own host. In this Robert Austrian Lecture for ISPPD14, Jeff will describe how quorum sensing resulting from competition among pneumococci contributes to inflammation that determines the outcome of pneumococcal pneumonia.

Jeff’s contributions to research are documented in 200+ manuscripts. Technology from his laboratory for expression of S. pneumoniae capsular polysaccharide has been licensed for production of a widely used pneumococcal conjugate vaccine. Additionally, Jeff has trained 20 thesis students, 27 post-doctoral fellows and 16 physician-scientists, from over 20 countries, many of whom are now independent investigators.

Shabir Madhi is the Dean of the Faculty of Health Sciences and Professor of Vaccinology at the University of the Witwatersrand, Johannesburg, South Africa. He also holds the position of Director of the South African Medical Research Council Vaccines and Infectious Diseases Analytics Research Unit (VIDA) and is co-Director of the African Leadership Initiative for Vaccinology Expertise (ALIVE).

He is an internationally recognised for his research on vaccines against life threatening disease in childhood, including against respiratory pathogens, as well as vaccines in pregnant women and people living with HIV. His research includes contributing to clinical development of vaccines against pneumococcus, respiratory syncytial virus, influenza virus, rotavirus, Group B streptococcus and Covid-19. He has supervised to comletion 30 PhD studnets and has published over 700 peer-reviewed articles, with a h-index of 103. He has been ranked in the top 1% of most cited researchers by Clavriate in 2024 and 2025. In 2024, he was co-recipient of Alert B Sabin Gold Medal for his contribution to the field of vaccinology.