The spread of COVID-19 is showing huge, unexplained, differences between northern and southern Italy. We hypothesized that the regional prevalence of specific class I human leukocyte antigen (HLA) alleles, which shape the anti-viral immune response, might partly underlie these differences. Through an ecological approach, we analyzed whether a set of HLA alleles (A, B, C), known to be involved in the immune response against infections, correlates with COVID-19 incidence. COVID-19 data were provided by the National Civil Protection Department, whereas HLA allele prevalence was retrieved through the Italian Bone-Marrow Donors Registry. Among all the alleles, HLA-A*25, B*08, B*44, B*15:01, B*51, C*01, and C*03 showed a positive log-linear correlation with COVID-19 incidence rate fixed on 9 April 2020 in proximity of the national outbreak peak (Pearson’s coefficients between 0.50 and 0.70, p-value < 0.0001), whereas HLA-B*14, B*18, and B*49 showed an inverse log-linear correlation (Pearson’s coefficients between −0.47 and −0.59, p-value < 0.0001). When alleles were examined simultaneously using a multiple regression model to control for confounding factors, HLA-B*44 and C*01 were still positively and independently associated with COVID-19: a growth rate of 16% (95%CI: 0.1–35%) per 1% point increase in B*44 prevalence; and of 19% (95%CI: 1–41%) per 1% point increase in C*01 prevalence. Our epidemiologic analysis, despite the limits of the ecological approach, is strongly suggestive of a permissive role of HLA-C*01 and B*44 towards SARS-CoV-2 infection, which warrants further investigation in case-control studies. This study opens a new potential avenue for the identification of sub-populations at risk, which could provide Health Services with a tool to define more targeted clinical management strategies and priorities in vaccination campaigns.

The adherence to the Mediterranean diet (MD) of 1740 Italian 8-9-year-olds was evaluated using the KIDMED index and a descriptive analysis of it by socio-demographic and lifestyle factors was performed. Only 5.0% of the children resulted "high" adherers of MD (62.2% "average" and 32.8% "poor"). This scarce adherence was due to a low consumption of fruit, vegetables, legumes, dairy products and a high intake of commercially baked goods for breakfast and sweets. Hindrances to fruit, vegetables and pulses consumption were reported for one-third of the sample. The adherence rates did not differ significantly with BMI and gender. Adherence improved with: having lunch at school; liking lunch at school; breakfast with family; no free access to food; availability of fruit and pulses; liking vegetables; higher maternal education; lower child screen time; population size of place of residence. The results show it is important to improve family food habits and dietary knowledge.