Seroprevalence study prior and post vaccination in cancer patients in principality of Andorra (COVONCO study).

Background: COVID-19 serologic response in patients with cancer may be lower than in the general population and may be influenced by the type of tumor or anticancer treatment. This study aims to analyze serological response prior and after vaccination of COVID-19 within the oncological population in Andorra. We set out to identify risk factors for a higher or lower serological response.

Patients And Methods: Observational, unicentric, prospective cohort study of oncologic patients in Andorra. We calculated the seroprevalence of antibodies against SARS-CoV-2 (May 2020-June 2021) and analyzed the main demographic, oncologic features and factors associated with being seropositive.

Results: A total of 373 patients were analyzed, mainly with solid tumours (n = 334, 89.5%). At baseline, seroprevalence was 13%, increasing during follow-up to 19%; lower seroprevalence was observed in patients with hematologic malignancies (2.6% vs 14.2%; p = 0.041) and patients receiving biological therapies (0% vs 15%, p = 0.005). In the overall seroprevalence analysis, women (23% vs 11.9%; p = 0.006) and tumour-free patients (p = 0.034) showed higher seroprevalence. The multivariable analysis showed that odds of being seropositive were higher among women (OR: 2.44, 95% CI 1.28-4.64), and patients who underwent surgery (OR: 3.35, 95% CI 1.10-10.20). About 80% of the cohort received at least one dose of COVID-19 vaccination, showing a higher seroprevalence of patients who received ChAdOx1-S than those who received BNT162b2 (24.4% vs 6.4%: p = 0.001).

Conclusion: The seroprevalence of antibodies against SARS-COV-2 in oncologic patients in Andorra was higher among females and patients who received hormonal therapy and surgery while patients with hematologic malignancies and biologic therapies showed lower seropositivity without finding differences in the type of tumour or anticancer treatment.