COVID-19 Antibody Response in Fully Vaccinated Patients With Cancer

Patients with cancer with complete COVID-19 vaccinations demonstrated a high rate of antibodies, according to the study.

Most patients with cancer in a recent study demonstrated an immune response to COVID-19 messenger RNA (mRNA) vaccines following their second dose. However, some patients in the study who were affected by certain cancers produced few or no antibodies, even after receiving both doses.1

This study, which was published in Cancer Cell, evaluated a cohort of 131 patients. The investigators studied the seroconversion rates or rates from a seronegative to a seropositive condition as well as the anti-COVID-19 spike protein antibody titers following the first and second dose of vaccines. This study was done from January to April 2021 in the United States and Europe.1

Messenger RNA (mRNA) vaccines, a new type of vaccine to protect against infectious diseases, are some of the first COVID-19 vaccines authorized for use in the United States. COVID-19 mRNA vaccines give instructions for our cells to make a harmless piece of what is called the “spike protein,” which is found on the surface of the virus that causes COVID-19. Patients with cancer experience a higher rate of COVID-19 infection and disease severity as well as complications and death rates compared with the general public. With other vaccines, patients with cancer have been known not to develop as robust an immune response as healthy individuals. However, there is little data on the effect of mRNA vaccines in this patient population.2,3

According to the study results, 94% of 131 patients with cancer achieved seroconversion of antibodies after the full 2 vaccine doses. Seroconversion rates were lower in those with blood and bone marrow cancers compared with those studied with tumors (77% versus 98%). The blood tests for antibodies were highest for endocrine therapy groups and lowest for chemotherapy monoclonal antibody groups. Patients receiving no therapy (ie, clinical surveillance) or endocrine therapy had the best outcomes, with high seroconversion rates (98%–100%) and excellent median antibody titer after completing vaccination series compared with significantly lower levels of antibody titers observed for those who received cytotoxic chemotherapy and monoclonal antibody therapy within 6 months before the first vaccine dose. No patients on the medication rituximab for types of cancer developed antibodies even after full vaccination.1

Additionally, the results of this study showed that the seroconversion rate after the full 2 doses was much higher than after only 1 dose.1,3 Women in the study had a higher positive antibody rate compared with men, but there were no other differences between sex, age, or race. There was no difference between vaccine types [Moderna or Pfizer] either in antibody tests in patients who had received 2 doses. A significant difference in antibody response was noted between the various anti-cancer treatment modalities as well.1

Research on the efficacy of COVID-19 vaccinations and optimal timing in relation to cancer treatment in this patient population is crucial because patients with cancer are at higher risk of serious COVID-19 complications. According to the study investigators, the findings confer that both doses of COVID-19 vaccines are necessary for robust antibody response, which underscores the added importance of adherence for this patient group. Moreover, the results suggest that patients receiving anti-CD20 antibodies continue to take precautions even after full vaccination, as they may be less likely to develop an immune response.1,3


1. Addeo A, Shah PK, Bordry N, et al. Immunogenicity of SARS-CoV-2 messenger RNA vaccines in patients with cancer. Cancer Cell. 2021. doi:10.1016/j.ccell.2021.06.009

2. Understanding mRNA COVID-19 Vaccines. Centers for Disease Control and Prevention. Updated March 4, 2021. Accessed July 6, 2021.

3. Sansom W. 94% of patients with cancer respond well to COVID-19 vaccines. UT Health San Antonio. Updated June 30, 2021. Accessed July 6, 2021.