Professor Tan has worked across the disciplines, and collaborated with scientists across Wellcome funded MIPs in Southeast Asia and Africa, in Oxford, the region, and beyond.

His early work focused on pathogen discovery, which led to the discovery of a novel cyclovirus in 4% of Vietnamese patients with encephalitis.

He is the principal investigator of Southeast Asia initiative to combat SARS-CoV-2 variants (SEACOVARIANTS) Consortium. SEACOVARIANTS aims to develop and apply a multidisciplinary research platform in Southeast Asia for rapid assessment of the biological significance of SARS-CoV-2 variants, thereby informing coordinated local, regional and global responses to the COVID-19 pandemic and emerging infectious disease outbreaks. Most recently, he was awarded multiple grants from Wellcome, UKRI, Singapore PREPARE and Vietnam NAFOSTED to develop novel serological tools to enable early detection of zoonotic spillovers, and to assess the local population immune landscape against highly pathogenic avian influenza A virus H5N1.