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The class of 2016 at the University of Minnesota in Minneapolis had an unusual first year. Amid studying and adjusting to life away from home, a number of students on the Minneapolis campus were giving blood samples and anonymously divulging whether they had been ‘deep kissing’ anyone to immunologist Hank Balfour and his team. The aim of the year-long study was to examine in detail the effect of infectious mononucleosis — also known as mono or glandular fever — on students who had not encountered it before, and to inform the design of a vaccine against it.