A large study published in the medical journal Cancer Cell on June 5 set out to determine how effective currently available COVID-19 vaccines are for cancer patients. Researchers used data from 200 eligible patients at Montefiore Health System and Albert Einstein College of Medicine in New York by testing their antibody levels after they were fully vaccinated. Results found that while most cancer patients in the study responded well to the shots, 30 percent of those taking immunosuppressant medications showed no signs of seroconversion, which is the medical term for the production of antibodies in response to a virus. RELATED: Half of People Who Did This Had No Antibodies After Vaccination, Study Says. The findings add to mounting evidence that the roughly six million Americans who rely on medications such as methotrexate, Rituxan, and certain steroids that suppress the immune system—which can be used to treat certain cancers, arthritis, psoriasis, and to stave off rejection of organ transplants—are not seeing the full effectiveness of their COVID-19 vaccines after regular dosages. It’s also added fuel to the argument that additional doses should be administered to immunocompromised people to shore up their immune response. “There should be already a national study looking at post-transplant patients getting booster shots,” Balazs Halmos, MD, an oncologist at the Montefiore Medical Center in New York City and the study’s lead author, told The New York Times. “It shouldn’t be our little team here in the Bronx trying to figure this out.” The use of a planned booster shot for such patients is already in practice in countries such as France. A study there found that while only 40 percent of immunocompromised patients had antibodies after two doses, it was increased to 68 percent four weeks after a third shot was administered. RELATED: If You Got This One Vaccine, Get a Booster Now, Virus Expert Warns. While Moderna and Pfizer are each planning studies on the use of a third dose in immunocompromised patients, some researchers argue that the slow pace of federal agencies is making it difficult to gather vital information. “It’s a very simple study,” Jose U. Scher, MD, a rheumatologist at NYU Langone Health who led a study of methotrexate’s effect on the vaccines, told The Times. “There’s no rocket science here.“ae0fcc31ae342fd3a1346ebb1f342fcb For now, the U.S. Centers for Disease Control and Prevention (CDC) advises that “antibody testing is not recommended to assess for immunity to SARS-CoV-2 following COVID-19 vaccination” as the results may not be accurate or helpful. The agency also says that “at this time, revaccination is not recommended after people who received COVID-19 vaccines during chemotherapy or treatment with other immunosuppressive drugs regain immune competence,” adding that their recommendations on additional shots may change when more information becomes available. RELATED: If You Got Moderna, This Is How Your Antibodies Respond to the Delta Variant.