[2] From 2006 to 2011, he was President of the United Kingdom's Academy of Medical Sciences, and since 2002 he has held the Regius Chair of Medicine at the University of Oxford.
[6] In 1982, despite lacking advanced scientific qualifications, he took up a position as Clinical Fellow in Immunology with Hugh McDevitt at Stanford University, where he worked on histocompatibility antigens and autoimmune disease.
[3][7][8] In 1987, Bell returned to Oxford as a Wellcome Trust Senior Clinical Fellow, and joined the Institute of Molecular Medicine, founded by David Weatherall.
[14] A BMJ campaign to make the results of unpublished studies on the anti-influenza drug oseltamivir (Tamiflu) available to researchers led to the journal's editor Fiona Godlee urging Bell "as an internationally respected scientist and clinician and a leader of clinical research in the United Kingdom, to bring your influence to bear on your colleagues on Roche's board.
Matthew Thompson and Carl Heneghan wrote in a letter to the journal "...according to Roche's 2011 financial report, John Bell received 390 000 Swiss Francs (£260 450; €322 450; $420 000) last year for his role on the board of directors.
His charity positions include chairing the board of trustees of the Oxford Health Alliance[8] and the science committee of the UK Biobank.
[19] A 2021 feature article by freelance journalist Paul D Thacker in the BMJ stated: "The government and Oxford University's failure to be open about Bell's financial ties make[s] it impossible for the public to know what, if any, interests the professor has when influencing key decisions about which of the many covid-19 tests the UK should purchase.
"[20] Bell has identified genes involved in susceptibility to diabetes mellitus type 1 and rheumatoid arthritis and multiple sclerosis.
He was appointed Knight Grand Cross of the Order of the British Empire (GBE) in the 2015 New Year Honours for services to medicine, medical research and the life science industry.