The conference and association services agency, Contendam, is to deliver full PCO services for the International Society for Influenza and other Respiratory Viral Diseases (ISIRV) conference in Chicago in 2016.
The conference is expected to attract 1,500 delegates.
Contendam and ISIRV have been in discussions for some time, with Contendam supporting the committee with the city selection process.
The second win for Contendam is the European Society for Surgical Research (ESSR) 2015 Conference, which will take place at Liverpool University in May 2015.
Susan Hayden, managing director of Contendam, said that the two new contracts are a result of "prolonged discussions with the relevant parties, rather than through the traditional or typical sales process."
She said: "It is great to see that our conscious efforts to engage, over long periods of time with people that we believe we can assist and truly add value to, is working."