ABSTRACT
OBJECTIVE: To compare seroconversion for SARS-CoV-2 receptor-binding domain (RBD) specific IgG positivity against two doses of the CoronaVac vaccine in breast and lung cancer patients receiving systemic therapy, to determine the factors affecting seropositivity, and to observe long-term results up to a secondary booster vaccine. RESULTS: The analysis included 201 cancer patients (99 breasts, 102 lungs; median age: 59 years (range: 28-92), 42.3 % men) and 97 controls (median age: 62 years (range: 24-87), 38.1 % men). The seropositivity rate for RBD IgG after 2 doses of vaccine in the cancer group was 81.6 % (n=164) and 93.8 % (n=91) in the control group (p=0.005). The median IgG titer of cancer patients was significantly lower than in the control group (338 (IQR, 95-933) AU/mL vs 676 (IQR, 389-1270) AU/mL; p<0.001). Multivariate analysis of all the patients determined that having cancer (OR: 0.303, 95%CI: 0.123-0.750, p=0.010) and being over 60 years of age (OR: 0.447, 95%CI: 0.218-0.917, p=0.028) was associated with a reduced vaccine response. A subgroup analysis of cancer patients revealed that seroconversion was lower in men than in women (75.3 % vs 86.2 %, p=0.049) and lower in ≥60 patients than in <60 patients (75.9 % vs 89.4 %, p=0.014). DISCUSSION AND CONCLUSION: Cancer patients receiving an active systemic therapy with two doses of the CoronaVac vaccine had a lower antibody response than the non-cancer population, and deaths due to COVID-19 may occur in these patients despite the vaccine. Therefore, extensive protective measures should be taken to protect against COVID-19 in cancer patients aged 60 years and older, who have received two doses of the CoronaVac vaccine (Tab. 4, Fig. 4, Ref. 27).