Inadequate Sars-Cov-2 Vaccine Effectiveness in Patients with Multiple Myeloma: A Large Nationwide Veterans Affairs Study

Introduction

Coronavirus disease 2019 (COVID-19), caused by the SARS-CoV-2 virus, is particularly serious in patients with multiple myeloma (MM), with estimated mortality of over 30% in several studies. In the general population, SARS-CoV-2 vaccination has been demonstrated to be an effective approach to preventing infection. However, patients with MM were not included in vaccination trials. Recent studies suggest that patients with compromised immune systems exhibit reduced antibody response to SARS-CoV-2 vaccination, and MM patients are often immunocompromised both due to MM itself and due to MM treatment. Thus, the objective of this retrospective cohort study in the national Veterans Affairs (VA) healthcare system was to evaluate the real-world effectiveness of SARS-CoV-2 vaccination to prevent COVID-19 infection in MM patients during the 140-day period following initial vaccine availability.

Methods

This is a multicenter study of SARS-CoV-2 infection among vaccinated and unvaccinated patients at VA hospitals nationwide during the period from 12/15/2020 to 5/4/2021. We identified a cohort of MM patients who were alive and without prior SARS-CoV-2 infection on their date of vaccination or inclusion as a control. For added comparison with a less immunocompromised population, we also identified a cohort of cancer survivors, defined as patients with any solid or hematologic malignancy who had been treated with systemic cancer-directed therapy subsequent to 8/15/2010, but had not been treated with such therapy in the 6 months prior to vaccination or inclusion as a control, and were alive and without prior SARS-CoV-2 infection on that date. Vaccinated patients were exactly matched 1:1 to unvaccinated controls on race, VA facility, rurality of home address, cancer type, and treatment timing and modality with minimum distance matching on age. The primary exposure was receipt of a SARS-CoV-2 vaccine. The primary outcome was laboratory-confirmed SARS-CoV-2 infection. Vaccination effectiveness was defined as 1 minus the risk ratio of SARS-CoV-2 infection for vaccinated individuals compared to unvaccinated controls.

Results

6,891 MM patients met eligibility criteria and 4,367 were vaccinated during the study period. Of those, 1,606 vaccinated MM patients were matched 1:1 to 1,606 unvaccinated or not yet vaccinated controls. In addition, for comparison, 2,476 vaccinated cancer survivors were matched 1:1 to 2,476 unvaccinated or not yet vaccinated controls. Median follow-up was 44 days among MM patients and 46 days among cancer survivors. Vaccine effectiveness in the matched cohort of MM patients was 22.2% (95% CI, -133 to 82.7%) starting 14 days after the second dose. In contrast, effectiveness was 82.3% (95% CI 16.4 to 100%) starting 14 days after the second dose in the matched cohort of cancer survivors. Among vaccinated MM patients in the matched cohort, 14 (8.7 per 1000 patients) were infected with SARS-CoV-2 subsequent to vaccination. Among vaccinated cancer survivors in the matched cohort, 10 (4.0 per 1000 patients) were infected subsequent to vaccination.

Conclusion

Vaccination is an effective strategy for preventing SARS-CoV-2. However, effectiveness may be reduced in patients with MM, likely due to a co-existing immunosuppression both due to the disease process as well as associated therapy. Future studies are needed to evaluate the relationship between MM disease states, types of therapy used and treatment timing that may impact vaccine effectiveness, and to also determine if MM patients would benefit from post-vaccination serologies or a booster vaccination.