Figures show Pacific and Māori children and young adults have the highest rates of rheumatic fever in New Zealand.
Victoria University's Dianne Sika-Paotonu and her fellow researchers will investigate how penicillin treatment has been working across different populations.
The initial studies were carried out on US soldiers in the 1950s.
Dr Sika-Paotonu has been awarded an extra 170-thousand US dollars to look into the issue.
She said it was clear better information was needed on how the drug works
