Analysis Suggests Patients with MPN Benefit from COVID-19 Vaccination

Patients with myeloproliferative neoplasms (MPN) appear to respond well to SARS-CoV-2 vaccination, according to a new report, with patients demonstrating high serologic and T-cell responses to the two most commonly administered vaccines.

The findings were reported in a letter to the editor of the journal Leukemia. Corresponding author Joan How, M.D., of Harvard Medical School, and colleagues, said while the SARS-CoV-2 vaccines developed by Moderna and Pfizer are widely successful at producing neutralizing antibodies in most adults, the vaccines have produced less robust immunologic responses in patients with hematologic malignancies.

Patients with MPNs “are immunocompromised due to impaired innate and adaptive immunity, heightened inflammation, and effects of ongoing treatment,” How and colleagues said. “As a result, patients are at high risk for complications related to SARS-CoV-2 infection.”

Given the novelty of the virus, the investigators wanted to get a better understanding of how the vaccines performed in real-world people with MPNs. They noted that most previous reports on vaccine protection in patients with hematologic malignancies focused on quantifying anti-spike antibodies. But they said T-cell responses are also a key metric for understanding immune response to vaccination.

“In particular, neutralizing antibody activity is significantly reduced against SARS-CoV-2 variants after vaccination, although T-cell responses still appear to be intact,” they wrote. “T-cell responses are therefore particularly important to prevent severe COVID-19 caused by emerging variants such as Omicron.”

The investigators recruited 21 patients with MPN who had baseline blood samples collected, completed vaccination with either the Moderna or Pfizer vaccines, and had a second blood sample taken one month following vaccination. Seven additional patients were included in the analysis despite having only a post-vaccination blood sample, and not a pre-vaccination sample. The authors used data from 26 vaccinated patients with no history of active malignancy as their control group. At baseline four of the 21 MPN patients had positive serology tests for SARS-CoV-2, and 3 patients had a known history of infection.

In both the MPN group (21 patients plus the additional seven patients), all but one vaccine recipient had evidence of positive serology a month after vaccination. The only patient who did not was on ruxolitinib (Jakafi). Similarly, 25 of the 26 patients in the control group had positive serology after a month.

“In the four MPN patients who had positive baseline serology, post-vaccination concentrations appeared similar to that of MPN patients without SARS-CoV-2 exposure,” the authors said.

How and colleagues also used two interferon γ-release assays to assess T-cell responses one month following vaccination.

On one of the assays, the ELISpot assay, positive responses greater than 90% were reported in both the MPN and control groups. However, the investigators also found that patients with MPNs tended to have lower anti-Spike immunoglobulin G concentrations, “which may indicate a less robust serological response,” they said.

Furthermore, the authors said, there appeared to be a signal for lower immunological responses in T-cell assays of patients with myelofibrosis, though the authors noted that that sample size was small, as just eight patients with myelofibrosis were included in the analysis. They added that age, but no other variables, seemed to have an effect on T-cell response.

How and colleagues said there were other subtle differences between the two groups, which may warrant further investigation. They concluded by noting that their samples may not necessarily reflect actual infection rates.

“Prospective studies with endpoints of clinical infection would be necessary to understand how immune responses to vaccines translate to reduction of COVID-19 cases,” they said.