Impact of chemotherapy and/or immunotherapy on neutralizing antibody response to
 SARS‐CoV
 ‐2
 mRNA
 ‐1237 vaccine in patients with solid tumors

Patients with solid tumors have been a risk group since the beginning of the SARS-CoV-2 pandemic due to more significant complications, hospitalizations, or deaths. The immunosuppressive state of cancer treatments or the tumor itself could influence the development of post-vaccination antibodies. This study prospectively analyzed 89 patients under chemotherapy and/or immunotherapy, who received 2 doses of the mRNA-1237 vaccine, and were compared with a group of 26 non-cancer individuals. Information on adverse events and neutralizing antibodies against the ancestral strain of SARS-CoV-2 (WH1) have been analyzed. Local reactions accounted for 65%, while systemic reactions accounted for 46% of oncologic individuals/cancer patients . Regarding the response to vaccination, 6.7% of cancer patients developed low neutralizing antibody levels. Lower levels of neutralizing antibodies between cancer and non-cancer groups were significant in individuals without previous SARS-CoV-2 infection, but not in previously infected individuals. We also observed that patients receiving chemotherapy or chemoimmunotherapy have significantly lower levels of neutralizing antibodies than non-cancer individuals. In conclusion, our study confirms the importance of prioritizing cancer patients receiving anticancer treatment in SARS-CoV-2 vaccination programs.