By Mike Bassett, MedPage Today Writer
Cancer patients who were vaccinated against COVID-19 achieved high rates of seroconversion, a single-center study found.
The seroconversion rate was especially high among patients with solid tumors (98%). However, patients with hematologic malignancies achieved lower rates (85%), particularly those who had undergone highly immunosuppressive therapies, reported Balazs Halmos, MD, MS, of Montefiore Medical Center in New York City, and colleagues.
Patients with hematologic malignancies also showed significantly lower titer levels compared with patients with solid tumors and cancer-free controls, according to findings from Cancer Cell.
"The message is that these vaccines are very safe and very effective for most cancer patients," Halmos told MedPage Today, adding that it may be necessary to develop different vaccination strategies for certain subsets of patients with hematologic malignancies.
"While the three FDA-approved vaccines, the mRNA-based mRNA-1273 (Moderna) and BNT162b2 (Pfizer/BioNTech) and the adenovirus-based Ad26.COV2.S (Johnson & Johnson), offer a high level of protection against the current circulating variants in the general population, limited data on their immunogenicity among patients with a cancer diagnosis are available," Halmos and colleagues wrote.
The authors reviewed 200 patients who underwent SARS-CoV-2 spike IgG testing after vaccination. Of these patients, 115 completed vaccination with the Pfizer injection, 62 with the Moderna vaccine, and 20 with the Johnson & Johnson single-dose injection. Information on the type of vaccine administered was unavailable for three patients.
The mean age of the patients was 67 years, and the cohort represented a racially diverse population, with 32% identifying as African American, 39% Hispanic, 22% Caucasian, and 5% Asian. There was no association between age or ethnicity and seroconversion rates.
Given that vaccine uptake has been low among African Americans and Hispanics, Halmos said it is important to note how well these patients fared with the vaccines.
Two-thirds of the patients in the study had solid tumors, while the other third had hematologic malignancies. Overall, the study population demonstrated a high seropositivity rate (94%), with only 6% of patients showing a negative value (titer below 50 AU/ml).
“We found the 94% rate very encouraging,” Halmos said. “Not only that, but when we looked at the antibody response titers, the average patient with a solid tumor had as good a response as the cancer-free controls.”
The seroconversion rates by vaccine type were 95% for the Pfizer vaccine, 94% for the Moderna vaccine, and 85% for the Johnson & Johnson vaccine.
The authors found no significant difference in seroconversion between patients receiving active cancer therapy (96%) and those not (93%). However, the seropositivity rate in patients receiving active cytotoxic chemotherapy (92%) was significantly lower compared to those not receiving it (99%).
A high seroconversion rate was observed among the 31 patients who received immune checkpoint inhibitor therapy (97%) and the 41 who received hormonal therapies (100%).
Among those who underwent immunosuppressive therapies, there were significantly lower seroconversion rates in the group of 26 patients who underwent stem cell transplantation (73%) and the 23 who underwent anti-CD20 therapies (70%). Furthermore, the three patients in the study who received CAR-T cell treatments remained seronegative after vaccination.
"These results highlighted the continued susceptibility of patients receiving these therapies during the pandemic," Halmos and colleagues noted.
Overall, vaccination appeared to be very safe in this cohort, with most anticipated adverse events (AEs) reported being mild to moderate. Across all 194 vaccination doses, no side effects were observed, and when adverse events such as arm pain and muscle aches were reported, they were no worse than among cancer-free controls.
The authors noted that their study highlights cohorts of at-risk patients, such as those with certain malignant hematological neoplasms.
“But we must remember that more than two-thirds of them developed an antibody response,” Halmos said. “That’s why they should be vaccinated according to the guidelines, which for most patients means as soon as they can, with the exception of bone marrow transplant patients, where it is recommended to delay vaccination for 3 months to allow for immune system recovery. These patients should continue to protect themselves with mask-wearing and social distancing, to some extent.”
“We should also consider research in these patients to see if we can devise vaccination strategies that might be more effective, such as additional booster shots or passive immunization strategies, like giving bone marrow transplant patients antibodies to protect them against COVID-19,” Halmos added. “But these are research strategies, not things we can recommend to patients at this time.”