Efficacy of SARS-CoV-2 vaccine in thoracic cancer patients: a prospective study supporting a third dose in patients with minimal serologic response after two vaccine doses.

Abstract Hypothesis Coronavirus disease 2019 (COVID-19) resulted in a 30% mortality rate in thoracic cancer patients. Given that cancer patients were excluded from serum anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) vaccine registration trials, it is still unknown whether they would develop a protective anti-spike antibody response following vaccination. This prospective vaccine monitoring study primarily aimed to assess humoral responses to SARS-CoV2 vaccine in thoracic cancer patients. Methods SARS-CoV2-spike antibodies were measured using Abbot ARCHITECT SARS-CoV-2 IgG immunoassay, prior to first injection of BNT162b2 mRNA vaccine, as well as at Week 4, and two-to-sixteen weeks after second vaccine dose. The factors associated with antibody response were analyzed. Results Overall, 306 patients, with a median age of 67.0 years (IQR=58-74), were vaccinated. Of these, 283 patients received two vaccine doses at 28-day intervals. After 6.7-month median follow-up, eight patients (2.6%) contracted proven symptomatic SARS-CoV-2 infection, with rapid favorable evolution. Of 269 serological results available beyond Day 14 post-second vaccine dose, 17 (6.3%) were still negative ( Conclusion SARS-CoV2 vaccines were shown to be efficient in thoracic cancer patients, most of them being immunized after two doses. A third shot given to 1% of patients with persistent low antibody titers resulted in a 88% immunization rate.