People whose immune systems are compromised by therapy or disease may benefit from additional doses of vaccines against SARS-CoV-2, researchers say.
In a study involving 101 people with solid-organ transplants, there was a significant boost in antibodies after the patients received third doses of the Pfizer vaccine, said Nassim Kamar, MD, PhD, professor of nephrology at Toulouse University Hospital, France.
None of the transplant patients had antibodies against the virus before their first dose of the vaccine, and only 4% produced antibodies after the first dose. That proportion rose to 40% after the second dose and to 68% after the third dose.
The effect is so strong that Dr. Kamar and colleagues at Toulouse University Hospital routinely administer three doses of mRNA vaccines to patients with solid-organ transplant without testing them for antibodies.
“When we observed that the second dose was not sufficient to have an immune response, the Francophone Society of Transplantation asked the National Health Authority to allow the third dose,” he told this news organization.
That agency on April 11 approved third doses of mRNA vaccines not only for people with solid-organ transplants but also for those with recent bone marrow transplants, those undergoing dialysis, and those with autoimmune diseases who were receiving strong immunosuppressive treatment, such as anti-CD20 or antimetabolites. Contrary to their procedure for people with solid-organ transplants, clinicians at Toulouse University Hospital test these patients for antibodies and administer third doses of vaccine only to those who test negative or have very low titers.
The researchers’ findings, published on June 23 as a letter to the editor of The New England Journal of Medicine, come as other researchers document more and more categories of patients whose responses to the vaccines typically fall short.
A study at the University of Pittsburgh that was published as a preprint on MedRxiv compared people with various health conditions to healthy health care workers. People with HIV who were taking antivirals against that virus responded almost as well as did the health care workers, said John Mellors, MD, chief of infectious diseases at the university. But people whose immune systems were compromised for other reasons fared less well.
“The areas of concern are hematological malignancy and solid-organ transplants, with the most nonresponsive groups being those who have had lung transplantation,” he said in an interview.
For patients with liver disease, mixed news came from the International Liver Congress (ILC) 2021 annual meeting.
In a study involving patients with liver disease who had received the Pfizer vaccine at Hadassah University Medical Center in Jerusalem, antibody titers were lower in patients who had received liver transplants or who had advanced liver fibrosis, as reported by this news organization.
A multicenter study in China that was presented at the ILC meeting and that was also published in the Journal of Hepatology, provided a more optimistic picture. Among patients with nonalcoholic fatty liver disease who were immunized against SARS-CoV-2 with the Sinopharm vaccine, 95.5% had neutralizing antibodies; the median neutralizing antibody titer was 32.
In the Toulouse University Hospital study, for the 40 patients who were seropositive after the second dose, antibody titers increased from 36 before the third dose to 2,676 a month after the third dose, a statistically significant result (P < .001).
For patients whose immune systems are compromised for reasons other than having received a transplant, clinicians at Toulouse University Hospital use a titer of 14 as the threshold below which they administer a third dose of mRNA vaccines. But Dr. Kamar acknowledged that the threshold is arbitrary and that the assays for antibodies with different vaccines in different populations can’t be compared head to head.