Humoral immune responses to the second dose of a COVID-19 mRNA vaccine in cancer patients undergoing treatment.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in 2020 led to the immediate development of vaccines to combat SARS-CoV-2 infections and coronavirus disease 2019 (COVID-19). First-generation (2020-2021) COVID-19 vaccines demonstrated high immunogenicity and efficacy, successfully reducing hospitalization, disease severity and COVID-19 related deaths. However, the initial clinical trials for these vaccines focused on overall healthy individuals, and generally excluded high risk populations, such as people with cancer. The SARS-CoV-2 VaccinE Response, Immunological eFfects and safetY in patients with Cancer (VERIFY-C) study formed a unique cohort in early 2021, to capture the initial immune response to BNT162b2 mRNA (Pfizer) vaccination in people with cancer, with or without ongoing/recent exposure to systemic cancer treatment. Fifty-three participants diagnosed with cancer were enrolled. Majority were non-Hispanic, Caucasian females. Patients under cancer treatment had significantly lower antibody responses than those without treatment at pre-second dose and 1-month post-second dose. The levels at 6-months post-second dose were similar between both groups. Patients under treatment had a significantly lower immune response 1-month post-second dose, with an increased immune response at 6-months post-second dose, suggesting a delayed immune response. Further investigations are needed to understand antibody functionality post-vaccination in these individuals.