She completed a Masters in Human Immunity at the University of Liverpool, where she was awarded a prize for being the best student of the year.

[2] Her thesis was entitled Immune responses to polymorphic antigens and protection against severe malaria in Kenyan children and was supervised by Kevin Marsh.

[8][9][10] In 2016 she won the Sofia Kovalevskaya prize from the Alexander von Humboldt Foundation, and moved to Universitat Heidelberg to continue her malaria research.

[11] Osier is interested in improving the prospects of African Scientists, and has her own research group in the Kilifi County District Hospital.

[13] Osier is a visiting professor at the University of Oxford, where she works in the Infection Immunology and Translational Medicine group.

In June 2022, Osier was appointed co-director of Imperial College London's Institute of Infection, where she is establishing a malaria research group.