To gain a better understanding of how immunocompromised people respond to the mRNA COVID-19 vaccine, researchers obtained blood samples from immunosuppressed, solid organ transplant recipients across the US. Transplant recipients who received an mRNA COVID-19 vaccination (Pfizer- BioNTech or Moderna) between December 16, 2020, and February 5, 2021 were recruited though social media. The time since transplantation was about 6 years and the maintenance immunosuppression regimens included tacrolimus (83%), corticosteroids (54%), mycophenolate (66%), azathioprine (9%), sirolimus (4%), and everolimus (2%).
Blood samples were taken about 20 days after the first vaccine dose. Among the 436 participants who received a first dose of an mRNA vaccine, only 17% had detectable antibodies to the SARSMay CoV-2 virus. For comparison, 100% of immunocompetent people who are vaccinated with mRNA vaccines have detectable antibodies after a first dose. The small percentage of transplant patients with detectable antibody levels had a few common factors: they were younger than 60 years old, they did not take anti-metabolites (eg, mycophenolate or azathioprine) for immunosuppression, and they received the Moderna vaccine.
The authors called on the CDC to update their guidelines so that immunosuppressed people can be warned that they may still be susceptible to COVID-19 after vaccination. These results may apply to other immunosuppressed patients, such as those with autoimmune conditions. The study is ongoing, and antibody responses will be measured following the second dose of vaccine.
For now, it’s important to tell immunocompromised people that they may not be immune following vaccination, and to consider antibody testing before relaxing preventive measures.