She founded the Vaccine Confidence Project at the London School of Hygiene & Tropical Medicine, which she still runs as of 2020, in addition to teaching anthropology, Risk and Decision Science.

[7][8][9][10][11][12][13] Since 2015, Larson has been leading a European Union project to support vaccination efforts in Sierra Leone, Rwanda, the Democratic Republic of the Congo and Uganda, identifying and countering rumours that may reduce the effectiveness of the campaign.

[14] Amid the COVID-19 pandemic, she co-chaired (alongside J. Stephen Morrison) the CSIS-LSHTM High-Level Panel on Vaccine Confidence and Misinformation in 2020.

[15] Describing herself as "a patient optimist", Larson understood early that significant efforts had to be made to fight misinformation about vaccines.

[7] In a paper published in February 2021, Larson acknowledged extensive collaboration with, advisory board membership of, and funding from, vaccine manufacturers, especially the pharmaceutical companies GlaxoSmithKline and Merck & Co. Inc.[16] She was recognized as one of the BBC's 100 women of 2021.