— Most patients on active treatment remained seropositive at 4 months

by Mike Bassett

Cancer patients on active treatment achieved sustained responses to the Pfizer/BioNTech COVID-19 vaccine, though at reduced antibody levels versus healthy controls, according to Israeli investigators.

After about 4 months from the second dose of Pfizer’s mRNA vaccine (BNT162b2), 87% of solid tumor patients who had been on active treatment remained seropositive for SARS-CoV-2 antispike IgG antibodies, reported Salomon M. Stemmer, MD, of Rabin Medical Center of Beilinson Hospital in Israel, and colleagues, in a research letter in JAMA Oncology.

Stemmer and colleagues noted that while the data are limited, studies have suggested durable responses after COVID-19 vaccination. They pointed out, for example, that results from an ongoing phase I trial of Moderna’s COVID-19 vaccine demonstrated that 6 months after vaccination, antibody activity remained high in 33 healthy adults from all age groups. But results in oncology patients specifically have been lacking.

The analysis from Stemmer’s group was a follow up to a previously published prospective cohort study that evaluated the rates of antibody response to the Pfizer’s vaccine in 102 cancer patients who were on active treatment compared with 78 healthy controls. A fourth of the patients were undergoing treatment for lung cancer, 26% for gastrointestinal cancers, and 18% for breast cancer. At that time, 90.2% of patients were found to be seropositive for SARS-CoV-2 antispike IgG antibodies, compared with 100% of the controls. However, the median IgG titer in cancer patients was significantly lower (1,931 vs 7,160 AU/mL).

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