Italian researchers performed a study to determine levels of antibodies developed by blood cancer patients following the first dose of the Pfizer vaccine. The study included 42 patients with multiple myeloma and 50 additional patients with myeloid cancers (CML and others). All patients on the study were on active cancer treatment and were compared to 36 elderly people who did not have cancer. 

The study reviewed antibody titer levels at 3 and 4 weeks after the first dose of the COVID vaccine was administered. The antibody test used was called the LIAISON® SARS-CoV-2 S1/S2 IgG test, which has been FDA approved.

At 5 weeks, the titer levels of the non-cancer elderly patients was 353 AU/mL compared to 106.7 in the myeloma patients and 172.9 in the myeloid cancer patients. The protection rate at a cutoff of 15 AU/mL was 100% in the control group compared to 78.6% in the myeloma group and 88% in the myeloid cancer group. Lower titers were found in older patients. Patients on daratumumab were less likely to develop antibodies. 

The researchers advised that patients on daratumumab should continue masking and social distancing regardless of their vaccination status and suggested that family members of these patients be vaccinated to reduce the risk of bringing COVID-19 home.

The Italian researchers also suggested that additional boosters and titer monitoring could be considered. The study was approved in January of 2021.