SARS-CoV-2 neutralizing antibodies (nAbs) decrease substantially 6 months after COVID-19 vaccination, particularly in patients with cancer, according to a study published in JAMA Oncology.
Roughly half of patients with hematologic cancers or solid tumors lost nAb responses to SARS-CoV-2 variants of concern at 6 months after vaccination. The same was true for 40% of healthy control individuals.
To evaluate humoral responses to COVID-19 vaccines, the researchers conducted a prospective study of 637 immunocompromised patients and 204 healthy control individuals.
The immunocompromised patients had solid tumor malignancies (n=399), hematologic malignancies (n=101), autoimmune diseases (n=99), or they had received a solid organ transplant (n=38). In the immunocompromised cohort, 391 patients (61.4%) were undergoing active systemic treatment at the time of vaccination.
In the entire cohort, 631 patients received the Pfizer-BioNTech COVID-19 vaccine, and 207 received the Moderna COVID-19 vaccine. Information on vaccine type was unavailable for 3 patients. All patients received 2 doses of the vaccines at 4 to 6 weeks apart.
The researchers measured nAbs against nonvariant SARS-CoV-2 as well as the alpha, beta, gamma, and delta variants at 1 week, 1 month, 3 months, and 6 months after COVID-19 vaccination.
Results: nAb Responses Over Time
At 1 month, nearly all healthy control individuals (95.7%-100%) had nAbs against nonvariant SARS-CoV-2 and the variants analyzed. The percentage of patients with nAbs was lower among patients with untreated solid tumors (84.9%-98.3%), treated solid tumors (80.1%-94.3%), untreated hematologic cancers (82.9%-92.7%), and treated hematologic cancers (49.0%-67.3%).
At 6 months, the proportion of patients with nAbs had decreased across all patient groups, and the greatest decreases were seen for nAb responses against the beta and delta variants.
The researchers analyzed nAb responses in 661 patients who had matched samples at 1 month, 3 months, and 6 months. The team assessed the magnitude of nAb responses as measured by IC50 dilutions greater than 50, which is the cutoff for a positive SARS-CoV-2 test result.
At 6 months, the percentage of patients with IC50 titers lower than 50 decreased for those with hematologic cancers (median, 39.2% for beta and 41.8% for delta), solid tumors (median, 44.8% for beta and 51.9% for delta), and healthy control individuals (median, 52.1% for beta and 56.9% for delta).
The researchers noted that nAb titers decreased 3.5- to 5-fold between month 1 and month 6, and nAb responses appeared more durable with the Moderna vaccine.
In patients with solid tumors, the estimated duration of nAb response against the beta variant was 221 days with the Moderna vaccine and 146 days with the Pfizer-BioNTech vaccine. For the delta variant, the estimated duration of nAb response was 226 days and 161 days, respectively.
In patients with hematologic malignancies, the estimated duration of nAb response was 113 days against the beta variant and 127 days against the delta variant. The researchers did not compare the 2 vaccine types in patients with hematologic cancers.
Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Obeid M, Suffiotti M, Pellaton C, et al. Humoral responses against variants of concern by COVID-19 mRNA vaccines in immunocompromised patients. JAMA Oncol. Published online March 10, 2022. doi:10.1001/jamaoncol.2022.0446
This article originally appeared on Cancer Therapy Advisor