COVID-19 vaccination lowers SARS-CoV-2 infection risk independent of diabetes, cancer and smoking in SHIP-COVID cohort, Northern Germany.

This study (n = 668) investigated the effect of vaccination on SARS-CoV-2 infection among individuals with type 2 diabetes mellitus (T2DM), cancer, and smoking in a prospective cohort study in Northern Germany. Participants from the SHIP-COVID cohort were followed from October 2020 to October 2022 using repeated questionnaires and serological tests. Infection was defined by anti-nucleocapsid (anti-NCP) antibodies' detection, self-reported Real Time Polymerase Chain Reaction (RT-PCR) or rapid antigen test. Vaccine efficacy was evaluated using risk differences (RD), risk ratios (RR), p-values, and 95% confidence intervals. Infection risk decreased with more vaccine doses; the 3rd (RR = 0.68) and 4th (RR = 0.29) doses offered significant protection. Both sexes showed protection with 3rd and 4th doses (RR = 0.67 and 0.20 in women and 0.68 and 0.39 in men, respectively). Logistic regression showed higher infection odds in individuals with T2DM (14%) and cancer (68% in SHIP-START-3 dataset and 45% in SHIP-START-4 dataset), while current smokers had 47% and 45% lower odds than non-smokers in SHIP-START-3 and SHIP-START-4 datasets respectively. No significant interactions were found between vaccination and T2DM, cancer, or smoking.