Parallel evolution and differences in seroprevalence of SARS-CoV-2 antibody between patients with cancer and health care workers in a tertiary cancer centre during the first and second wave of COVID-19 pandemic: canSEROcov-II cross-sectional study

BACKGROUND: Patients with cancer are a population at high risk of severe infection from SARS-CoV-2. Patients with cancer regularly attend specialised healthcare centres for management and treatment, where they are in contact with healthcare workers (HCWs). Numerous recommendations target both patients with cancer and HCWs to minimise the spread of SARS-CoV-2 during these interactions. OBJECTIVE: To investigate the parallel evolution of the COVID-19 epidemic in these 2 populations over time, we studied the seroprevalence of anti-SARS-CoV-2 antibodies after both the first and second waves of the pandemic, and in both cancer patients and HCWs from a single specialised anti-cancer centre. Factors associated with seropositivity were identified in both populations. METHODS: We conducted a cross-sectional study after the second wave of the COVID pandemic in France. All participants were invited to undergo serological testing for SARS-CoV-2 and complete a questionnaire collecting data about their working conditions (for HCWs) or medical management (for patients) during this period. Results after the second wave were compared to those of a previous study among 1011 patients with cancer and 663 HCWs performed in the same centre after the first wave, using the same evaluations. FINDINGS: We included 502 HCWs and 507 patients with cancer. Seroprevalence of anti-SARS-CoV-2 antibodies was higher after the second wave than after the first wave in both HCWs (15.1% versus 1.8%; p < 0.001), and patients (4.1% versus 1.7%; p = 0.038). By multivariate analysis, the factors found to be associated with seropositivity after the second wave for HCWs were: working in direct patient care (p = 0.050); having worked in a dedicated COVID-19 unit (p = 0.0036); contact with a person with COVID-19-positive in the workplace (p = 0.0118) or outside of the workplace (p = 0.0297). Among patients with cancer, only a contact with someone who tested positive for COVID-19 was found to be significantly associated with positive serology. The proportion of reported contacts with individuals with COVID-19-positive was significantly lower among patients with cancer than among HCWs (7.6% versus 40.7%, respectively; p < 0.0001) INTERPRETATION: Between the first and second waves of the epidemic in France, the seroprevalence of anti-SARS-CoV-2 antibodies increased to a lesser extent among patients with cancer than among their HCWs, possibly due to better self-protection, notably social distancing. The risk factors for infection identified among HCWs plead in favour of numerous intra-hospital contaminations, especially for HCWs in contact with high-risk patients. This underlines the compelling need to pursue efforts to implement strict hygiene and personal protection measures (including vaccination) to protect HCWs and patients with cancer.