People with conditions that compromise their immune systems exhibit a wide spectrum of antibody responses to COVID-19 vaccination, ranging from only one in five lung transplant patients having an antibody response to a nearly complete response in patients with well-controlled HIV, according to results from an interim analysis of a large study on University of Pittsburgh Schools of the Health Sciences (UPMC) patients and healthcare workers, reported the university.
The study is one of the first to verify that the ability of blood from immunocompromised participants to neutralize the virus closely mirrors their antibody levels measured by a U.S. Food and Drug Administration (FDA)-approved test, meaning that antibody testing is a good proxy for neutralizing titers.
In an effort to share crucial information to guide clinical and public health decisions, UPMC and University of Pittsburgh School of Medicine physician-scientists published the findings in medRxiv, a preprint journal, and announced the results ahead of peer-reviewed publication. Between April 14 and June 14, the UPMC-Pitt team tested blood samples from 107 healthy volunteer healthcare workers and 489 immunocompromised patients who had completed COVID-19 vaccination as part of the COVID-19 Vaccine in the Immunocompromised Study (CoVICS). The immunocompromised patients included those who had a solid organ transplant, an autoimmune disorder, blood cancer, a solid tumor cancer or HIV.
Antibodies are proteins that block invading pathogens—such as SARS-CoV-2, the virus that causes COVID-19—from infecting cells. They are produced by the immune system in response to vaccination. While 98.1% of the healthcare workers produced antibodies after vaccination, only 37.2% of the vaccinated solid organ transplant patients were positive for antibodies; 54.7% of the blood cancer patients; 82.4% of those with solid tumor cancer and 83.8% of patients with autoimmune disorders. In contrast, 94.6% of patients with HIV made antibodies.
Among patients with solid organ transplants, lung transplant patients had a particularly poor response to vaccination, with only 22.2% producing antibodies. Liver transplant patients fared best, with 60.6% of study participants producing antibodies after vaccination. Patients who received their transplant less than a year ago were less likely to respond to vaccination than those transplanted earlier.
In addition, cancer patients receiving radiation therapy and patients taking certain medications—such as antimetabolites for transplant and anti-CD20 monoclonal antibodies for autoimmune disorders—were more likely not to produce antibodies after COVID-19 vaccination.
The researchers then took blood sera, the amber-colored, protein-rich liquid that separates out when blood coagulates, from a subset of the participants — 30 healthcare workers and 36 immunocompromised patients — and tested it for its ability to neutralize SARS-CoV-2. They found that the ability of the participants’ sera to neutralize the virus correlated strongly with their antibody levels measured by an independent FDA-approved test.
