Evaluating antibody response rates of patients with chronic lymphocytic leukemia to a third dose of mRNA COVID-19 vaccine

This study aimed to investigate the antibody response to a third mRNA COVID-19 vaccine of patients with chronic lymphocytic leukemia (CLL) who had failed to achieve an antibody response after the standard two-dose vaccination regimen. 

This study concluded that approximately a quarter of patients responded to the third vaccine.  

CLL is a cancer of immune cells in the blood. It is associated with impaired immune responses to infections such as COVID-19. Treatments of CLL are also associated with lower immune responses. Therefore, patients with CLL are recommended to get the COVID-19 vaccines for protection. However, patients with CLL have been shown to have an impaired antibody response to the standard 2-dose COVID-19 vaccination regimen. 

It was unknown what percentage of patients with CLL would respond to the third mRNA COVID-19 vaccine.  

This study involved 172 patients with CLL. All patients received a standard 2-dose mRNA COVID-19 vaccine regimen and did not produce any antibodies. Patients received the third dose of the mRNA COVID-19 vaccine. Anti-SARS-CoV-2S and neutralizing antibodies were measured 3 weeks after the administration of the third dose of the vaccine.  

The overall antibody response rate was 23.8%. Untreated patients and those off-therapy, as well as patients who were 12 months or more from their last anti-CD20 (a type of immunotherapy such as rituximab/Rituxan), were significantly more likely to have an antibody response. There was a slightly higher percentage of patients younger than 65 years who responded to the third dose compared to those over 65 years of age. 

The antibody response rate in actively treated patients was 12% compared to 40% in untreated patients. The rate in patients off-therapy was 40.6%.  

55.4% of patients had local reactions to the third dose such as pain at the injection site, redness, or swelling. 26.8% of patients reported mild whole-body side effects such as tiredness, muscle pain, or fever. 

This study concluded that in patients with CLL who failed to achieve antibody response after standard two-dose mRNA COVID19 vaccination regimen, close to 25% responded to the third dose of vaccine. It was also concluded that antibody response rates were lower during active treatments and in patients with a recent exposure (<12 months prior to vaccination) to anti-CD20 therapy. 

This study did not compare antibody response to healthy individuals.