Background: Vaccines have shown 95% protection from COVID-19 disease in healthy populations. Initial findings in cancer patients suggest a lower seroconversion and greater toxicity possibly related to myelo-immunosuppressive therapies.
Aim: We conducted a prospective study to assess factors predicting poor seroconversion and adverse events following immunization (AEFI) to the BNT162b2 vaccine in cancer patients on active treatment.
Methods: Blood samples were collected by the research nurse at first dose (visit 1), second dose (visit 2), after 42 days (visit 3) and after 6 months (visit 4). At visit 1, 3 and 4 participants received: Hospital Anxiety and Depression Scale (HADS) and Distress Thermometer. Patients who ended treatment >6 months on active surveillance served as controls.
Results: Between March and July 2021, 320 subjects were recruited and 291 were assessable. The lack of seroconversion at 21 days from the second dose was 1.6% (95% CI, 0.4-8.7) on active surveillance, 13.9% (8.2-21.6) on chemotherapy, 11.4% (5.1-21.3) on hormone therapy, 21.7% (7.5-43.7) on targeted therapy and 4.8% (0.12-23.8) on immunotherapy. Compared to controls, the risk of no IgG response was greater for chemotherapy (P=0.033), targeted therapy (0.005) and hormonotherapy (P=0.051). Lymphocyte count less than 1x109/L, older age and advanced stage also significantly predicted poor seroconversion. Overall, 43 patients (14.8%) complained of AEFI, mostly of mild grade. Risk of AEFI was greater in females (P=0.001) and younger patients (P=0.009).
Conclusions: A third booster dose and long-term serological testing is required in subjects who have not responded to the vaccine.
Nursing implications: nurses must take responsibility for promoting and protecting the health of cancer patients.