Patients Have Higher COVID-19 Risk Even if Fully Vaccinated: US Study

Marta Figueiredo, PhD avatar

by Marta Figueiredo, PhD |

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Even if they’re fully vaccinated, multiple myeloma patients still have an increased risk of COVID-19 infection compared with people without cancer, according to a study looking at data from more than 500,000 individuals in the U.S.

Called breakthrough infections, these post-vaccination illnesses from SARS-CoV-2 — the virus that causes COVID-19 — also were associated with a higher risk of all-cause hospitalization among myeloma patients.

“The overall risk of SARS-CoV-2 breakthrough infections was 15.4% in the MM [multiple myeloma] population and 3.9% in the noncancer population,” the researchers wrote, noting that these cancer patients had an estimated probability of hospitalization of nearly 35%.

These findings call for better mitigation strategies and appropriately-designed studies evaluating the effects of vaccine boosters in this immunosuppressed patient population, the researchers noted.

The study, “Risks of SARS-CoV-2 Breakthrough Infection and Hospitalization in Fully Vaccinated Patients With Multiple Myeloma,” was published as a research letter in the journal JAMA Network Open.

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COVID-19 vaccines work by training the body’s immune system to recognize SARS-CoV-2, allowing a faster and more potent immune response in case of an infection, with the potential to prevent severe disease.

As such, these vaccines may not work as well in people who have a weaker immune system, either due to disease or the use of immunosuppressive treatments — as is the case for multiple myeloma patients.

Previous studies have shown that people with myeloma are indeed at a greater risk of SARS-CoV-2 infection than those without cancer, and that they show poor immune responses to COVID-19 vaccines.

While these findings highly suggest that myeloma patients may be more vulnerable to SARS-CoV-2 breakthrough infections, the risk and outcomes of such infections remain unknown in this patient population.

To learn more, a team of researchers at Case Western Reserve University’s School of Medicine, in Ohio, analyzed the de-identified health electronic records of 507,288 fully vaccinated people who had appointments at one of 63 U.S. healthcare organizations after Dec. 1, 2020. None had records of prior SARS-CoV-2 infection.

Data, accessed through a cloud-based platform called TriNetX, were used to evaluate whether myeloma patients had a higher risk of breakthrough SARS-CoV-2 infections than people without cancer, even after full vaccination.

Researchers also assessed whether hospitalization rates differed between myeloma patients with and without breakthrough infections.

The 1,182 people with a multiple myeloma diagnosis had a mean age of 68, while the 506,106 people with no record of cancer had a mean age of 51.3. Most people in both groups received the Pfizer-BioNTech vaccine, sold as Comirnaty (77% in the myeloma group and 90.1% in the non-cancer group). In the myeloma group, 22.2% had the Moderna vaccine.

Most (88.7%) myeloma patients had never achieved remission, while 33.8% had monoclonal gammopathy of undetermined significance — a nonactive form of myeloma — and 11.7% were experiencing disease relapse.

Their mean number of lymphocytes, a type of immune cell, in the blood was within the normal range, but much closer to the lower limit.

Chemotherapy was the most commonly used cancer treatment (60%), followed by targeted therapy (50.3%), stem cell transplant (26.5%), and radiotherapy (12.1%).

The results showed that myeloma patients had a nearly four times higher risk of breakthrough SARS-CoV-2 infection compared with people without cancer (15.4% vs. 3.9%).

When the myeloma group was compared with a non-cancer group matched for potential influencing factors — such as demographics, simultaneous health conditions, vaccine types, and medications — people with myeloma still had a 34% greater risk of breakthrough infection.

In addition, after infection, myeloma patients had a 34.4% risk of all-cause hospitalization, while the post-vaccination risk for those who were not infected was only 4.5%, reflecting a nearly 16 times higher risk.

These findings highlight that people with multiple myeloma are at an increased risk of SARS-CoV-2 infection even after full vaccination and that these breakthrough infections are linked to a higher likelihood of subsequent hospitalization.

The results “raise consideration for the development and implementation of enhanced mitigation strategies and the need for studies to evaluate the timing and impact of vaccine boosters in this unique, immunosuppressed population,” the researchers wrote.

The researchers noted, as a limitation, that the study was observational, but said the database used allowed them to monitor “the risks and outcomes of vaccine breakthrough infections in a real-world vulnerable population (ie, patients with MM [multiple myeloma]).”

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