[2] An infectious disease specialist and researcher, Walker is the founding director of the Ragon Institute of Mass General, MIT, and Harvard.

[3] He played an active role in COVID-19 research, helping found and co-lead the Massachusetts Consortium on Pathogen Readiness (MassCPR) and advance vaccine development with the Ragon Institute.

They led Walker to specialize in infectious disease and begin researching HIV in the laboratory, to understand how the body fought back and why it often lost the battle.

[14][15] Before effective antiretroviral therapy was available, Walker met a patient with hemophilia who had been infected with HIV through a blood product in 1978 but never developed AIDS.

This experience initiated a career of learning from patients, inspiring subsequent research into "elite controllers," the less than 1 percent of people living with HIV who remain healthy, without medication, decades after infection.

The second goal is to identify persons in the window period before peak viremia and seroconversion (defined by Fiebig Stages I-VI), to determine how the battle between host and virus begins.

[18][19] Through this study, Walker and colleagues have determined that the higher initial magnitude of the HIV-specific T cell response, the lower the viral set point in untreated infection.

The initial plan had been to find collaborators in South Africa, hardest hit by the AIDS epidemic, to study immune responses in babies born with HIV infection, who typically have very rapid disease progression.

The stated goal was to bring samples back to the US, but the African collaborators, led by the late Jerry Coovadia, asked Walker and colleagues to consider doing the studies in Durban and teach them to conduct fundamental research.

This led to a brief conversation between Walker and Ragon, followed by a short trip to KZN to see the EMR in action and to get a view of the ongoing HIV epidemic.