Preliminary research conducted on a small sample size suggests that certain COVID-19 vaccines, including Pfizer and Moderna, may not be effective for solid organ transplant patients and others with compromised immune systems.
A team of Mayo Clinic researchers studied seven organ transplant recipients diagnosed with COVID-19 at Mayo Clinic in Jacksonville six to 44 days after receiving the Moderna or Pfizer vaccines. Two patients had received just one dose and the remaining five had received both doses.
The Johnson & Johnson vaccine was not reviewed by Mayo researchers in this study because it was not available to Mayo patients at the time.
The researchers, led by Mayo Clinic Transplant Center Nephrologist Dr. Hani Wadei, confirmed all of the patients were infected with COVID-19 with five suffering severe symptoms that required hospitalization. Three of those patients even needed oxygen when they were discharged.
Some of those patients had their transplant procedure years ago.
"This study is eye-opening for the transplant community," said Wadei. "Our study suggests that transplant patients don't have the same immune response as the general population. They got infected after getting vaccinated and lifting protective measures, thinking they were immune to the virus."
Vaccines work by imitating an infection and causing the immune system to produce antibodies. Those antibodies help fight the disease in the future.
However, transplant patients are placed on anti-rejection or immunosuppressive medications after their procedures. These medications are designed to decrease the efficiency of the immune system so that patients don’t reject their transplanted organs, but they also appear to significantly decrease the efficiency of the Pfizer and Moderna vaccines and leave the patients more vulnerable to infection.
Many transplant patients need to have their immune systems suppressed for about a year. Others may need to be immunosuppressed for the rest of their lives.
“Because your immune system is decreased, it places you at higher risk of catching infections and it also decreases your ability to form antibodies once you're exposed to a specific infection,” explained Mayo Clinic Transplant Pulmonologist Dr. Sadia Shah, another researcher who worked on the study.
The research team estimates that the infection rate in vaccinated solid organ transplant recipients is 10 times higher than the general population — 0.6% versus 0.05%.
Shah warns that it’s hard to make decisions based on findings from such a small sample size, which is why she’s leading a larger study looking at all of Mayo Clinic’s solid organ transplant patients to determine what percentage actually do develop an antibody response to the COVID-19 vaccines. Eventually, the study will expand to include transplant patients at Mayo’s other campuses in Arizona and Minnesota.
Until the efficacy of vaccines among this population is better understood, Shah and Wadei said it’s critical for everyone to continue to take precautions.
“All individuals, especially transplant patients, should continue to follow protective measures, such as social distancing, mask-wearing and regular hand hygiene,” said Wadei
“You have to have herd immunity for the vaccination to be effective and right now we’re not at that status where we have that herd immunity,” warned Shah.
Even if the larger study supports the findings of this preliminary research, Shah said it’s crucial that all transplant patients get vaccinated.
“For the patients who are unable to develop antibodies, we have means to help increase their chances of developing antibodies,” she said. “We can do that by potentially decreasing their immunosuppression for a very short period of time and giving them a booster vaccine.”
The findings of Mayo Clinic’s preliminary research were published as a letter to the editor in the American Journal of Transplantation.