In a recent study, African-Americans ages 30- to 40-years-old presented with higher levels of antibodies to the H1N1 virus than Caucasians of the same age. However, this disparity appears to decrease with age because the same study showed no difference in antibody levels among adults of any ethnicity over the age of 65.

References:

Kurupati R, Kossenkov A, Haut L, et al. Race-related differences in antibody responses to the inactivated influenza vaccine are linked to distinct pre-vaccination gene expression profiles in blood. Oncotarget. 2016;7(39):62898-911.

Singh B. Ethnicity Influences Response to Influenza Vaccine. Sci-news website. http://www.sci-news.com/medicine/ethnicity-influences-response-influenza-vaccine-04313.html. Published online October 27, 2016.