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Although breakthrough COVID-19 infections appear to be infrequent in people with inflammatory rheumatic and musculoskeletal diseases (iRMDs), these patients’ comparatively low antibodies after their initial vaccine series validate the recommendation that booster doses could reinforce their immune responses. These findings were highlighted in three letters recently published in Annals of the Rheumatic Diseases.

In the first letter, the researchers assessed breakthrough COVID-19 infections among vaccinated patients with iRMDs who were treated within the Mass General Brigham health care system in the Boston area. Of the 340 COVID-19 infections in patients with iRMDs after vaccinations were approved by the Food and Drug Administration for emergency use, 16 (4.7%) were breakthrough infections. All but one of the breakthrough infections were symptomatic, and six of the patients were hospitalized.

Patients who had breakthrough infections took disease-modifying antirheumatic drugs (DMARDs) that included rituximab and glucocorticoids (five patients each), mycophenolate mofetil or mycophenolic acid (four patients), femara 2.5 mg letrozole and methotrexate (three patients). Two of the patients died, both of whom were on rituximab and had interstitial lung disease.

“Some DMARD users may require alternative risk-mitigation strategies, including passive immunity or booster vaccines, and may need to continue shielding practices,” the authors wrote.

Dr Camille Kotton

“Honestly, it’s hard to know what to make of that rate of breakthrough infections,” Camille Kotton, MD, clinical director of transplant and immunocompromised host infectious diseases in the infectious diseases division at Massachusetts General Hospital in Boston, said in an interview. “People who are immunocompromised were strongly advised to change behavior so as to avoid infection, which probably greatly alters their risk of breakthrough infection. It’s thus hard to evaluate vaccine efficacy.

“Also, 93% were symptomatic, which is fairly high,” she added. “I’m not sure if these patients were more likely to be symptomatic or if there was some bias in testing based on symptoms.”

In the second letter, the researchers assessed postvaccination COVID-19 infections in European patients with iRMDs. Two COVID-19 registries with thousands of patients were reviewed, with less than 1% of patients in each deemed eligible for this study. Of the 34 patients who were ultimately analyzed with available COVID-19 outcomes – 10 were fully vaccinated and 24 were partially vaccinated – 28 fully recovered, 3 recovered with ongoing sequelae, and 3 patients died. The three patients who died were all over 70 years old and had been treated with glucocorticoids and mycophenolate mofetil, glucocorticoids, and rituximab, respectively.

The medications most frequently used by the iRMDs patients with breakthrough cases included glucocorticoids (32%), methotrexate (26%), and tumor necrosis factor inhibitors (26%).

“Overall, the low numbers of SARS-CoV-2 infection post vaccination in both registries are encouraging,” the authors wrote, adding that “all three deceased patients were treated with medications that are potential negative influences on postvaccination SARS-CoV-2 immunogenicity in the RMD population.”

Patients With RMDs: Consider COVID-19 Booster Shots

In the third letter, the researchers investigated booster doses of COVID-19 vaccine in patients with autoimmune diseases. Of the 18 participants who received a booster dose, 14 were on antimetabolite therapy and 8 of those were on mycophenolate. At a median of 29 days after completion of their initial vaccine series, antispike antibodies were negative in 10 of the participants and low positive in 6 others, with a median antispike antibody level of less than 0.4 U/mL (interquartile range, <0.4-222 U/mL).

Booster doses were administered at a median of 77 days after completion of the initial series. At a median of 30 days after booster dose, 89% of the participants had an augmented humoral response, with a median antispike antibody level of 2,500 (IQR, 885-2,500 U/mL). Of the 10 participants who had negative anti-spike antibodies after the initial series, 80% were positive after the booster.

Dr Julie Paik

“I think this study supports the wealth of evidence that contributed to the [Centers for Disease Control and Prevention]’s and the FDA’s recommendation to get the third dose of the COVID vaccination,” coauthor Julie J. Paik, MD, of Johns Hopkins University, Baltimore, said in an interview. “Our patients are a very vulnerable group, including lupus patients or myositis patients, both of whom can get severe COVID if they were to contract it. They think they’re protected after a two-dose series, but in reality they’re not.

“We were just happy that they had a response,” she added. “Most of them had absolutely no response whatsoever after the first series.”

One other recently published case report in Arthritis & Rheumatology describes booster vaccination with the viral vector Johnson & Johnson vaccine in a man with seropositive RA who had previously received both doses of the Moderna mRNA-1273 vaccine.

The 74-year-old man, who had low disease activity over the past 5 years on hydroxychloroquine, etanercept, and leflunomide, received the booster dose of his own accord after undergoing testing that showed a semiquantitative spike protein receptor binding domain (RBD) antibody level of 53.9 U/mL (reference range, 0-2,500 U/mL) and a negative SARS-CoV-2 antispike (S1/RBD) IgG test, as well as less than 10% blocking activity on an assay designed to detect blocking of the interaction between the SARS-CoV-2 spike protein RBD and the human ACE2 receptor and a negative interferon-gamma release assay detecting SARS-CoV-2–specific T cells.

Several weeks after the booster dose, a repeat semiquantitative spike protein RBD antibody level was 2,455.0 U/mL and the S1/RBD IgG level was positive. An ACE2 blocking assay demonstrated 90%-100% blocking activity, but the interferon-gamma release assay remained negative.

“I would recommend abiding by the CDC guidelines regarding boosters for immunocompromised patients,” Kotton stated. “Patients with rheumatologic disease generally fit into the last category on that list. We don’t have an antibody titer that ensures protection, and as per CDC guidance, we don’t recommend checking antibody titers. Furthermore, boosters were given for this study before the CDC recommendation came out.”

Paik and coauthors acknowledged their study’s limitations, including a small, inhomogeneous sample and a lack of data on memory B-cell and T-cell response. They also echoed Kotton’s thoughts by noting that, although this subset of patients had notably limited antibody responses, “no antibody titer has been defined to correlate with protection.”

“Of course, the humoral response isn’t the whole story,” Paik said. “Some studies are showing that some vaccine recipients may not have the antibodies but their T-cell response may still be intact; it just takes time, and we’re not picking it up. Even if the antibody test is coming up negative, there may be some immunogenicity to the vaccine that we’re not detecting.

“Hopefully at some point, we’ll have more T-cell immunophenotyping to provide better insight into the full vaccine response.”

The Boston-area breakthrough study and the booster shot study were both funded primarily by grants from various institutes within the National Institutes of Health. The European study was financially supported by the European Alliance of Associations for Rheumatology.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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