[6] In 2012, he finished his Ph.D. in Medicine in Barcelona; his thesis was entitled "Strategies for the control of the yaws and other neglected tropical diseases of the South Pacific islands" and was based on his on-site research at the Lihir medical center in Papua New Guinea.

He conducted a randomized trial that was published in 'The Lancet' [8] that revealed that a single-dose oral azithromycin is effective to cure yaws and is easier and safer to administer as compared to the standard treatment with injectable penicillin.

Mitjà is conducting research to advance knowledge in the field of therapeutics, where he aims at repurposing existing therapies to reduce the risk of infection with the SARS-CoV-2 coronavirus.

Mitjà is also conducting research in the field of diagnostics, where he is assessing the validity of Rapid antigen tests to facilitate massive screening of the population, and in the areas of transmission and risk factors.

In 2012, Mitjà was awarded the Swiss Foundation Anne-Maurer Cecchini prize as a result of the publication of the aforementioned study re yaws in The Lancet In 2013, he was awarded the Prince of Girona Foundation[10] for Scientific Research for his "exemplary dedication in the field of endemic infectious diseases in developing countries and the great international impact of his work aimed at eradicating yaws disease of the planet".