Objective  To investigate the incidence of COVID-19 in patients with tumor during the pandemic of Omicron variant strains.

  Methods  From December 25, 2022 to January 25, 2023, through the questionnaire star platform in the form of electronic questionnaire, we collected information about COVID-19 vaccine, COVID-19 infection and clinical symptoms, and post-infection anti-tumor therapy of patients with malignant tumors (including patients who previously visited the oncology department of Peking Union Medical College Hospital and the oncology department of the local hospital where the trainee doctors of the oncology department of Peking Union Medical College Hospital are located) during the survey period (from December 9, 2022 to the time of questionnaire survey) and performed statistical analysis.

  Results  A total of 270 questionnaires were sent out, of which 265 valid questionnaires were recovered (the effective questionnaire rate was 98.1%). Among the 265 patients with malignant tumors, 170(64.2%) patients received COVID-19 vaccine, 158(59.6%) patients were alive with tumor, and 216 patients (81.5%) were receiving antitumor therapy at the time of COVID-19 infection or during the investigation. In 210 cases (79.2%), patients were infected with COVID-19. Among them, 9 cases (4.3%) developed COVID-19 pneumonia and 3 cases (1.4%) were hospitalized due to COVID-19, and there were no severe or fatal cases. Among the infected patients, 205(97.6%) patients showed symptoms related to the COVID-19, among which fever was the most common (72.9%) symptom, and cough (64.8%) and sputum (50.5%) were the main respiratory symptoms. There were no significant differences in gender, age, tumor type, whether they had underlying diseases, whether they were vaccinated against COVID-19, and whether they were treated with anti-tumor therapy between COVID-19 infected and uninfected patients (all P > 0.05). Among the infected patients, the incidence of pneumonia in those who received ≥3 doses of vaccine was significantly lower than that in those who did not receive vaccine (1.1% vs. 9.9%, P=0.025). At the time of questionnaire survey, 88 patients started antitumor therapy after COVID-19 infection. Compared to infection before COVID-19, 12 patients(13.6%) had more serious adverse anti-tumor reactions after COVID-19 infection, 63 patients (72.7%) had similar symptoms, and 12 patients (13.6%) had milder symptoms. There was no significant correlation between the adverse reactions of anti-tumor therapy before and after infection and the timing of initiation of anti-tumor therapy after infection(P=0.938), but there was a certain correlation with anti-tumor therapy after infection(P=0.003).

  Conclusions  During the pandemic period of Omicron variant, tumor patients were generally susceptible to COVID-19. Almost all infected patients showed related clinical symptoms, but very few patients developed pneumonia. Vaccination with≥3 doses of vaccine may be protective against pneumonia. The adverse reactions of anti-tumor therapy in most cancer patients after infection with COVID-19 were not significantly worse than those before infection.