COVID-19: Are Transplant Patients at Higher Risk of Reinfection Even After Full Vaccination?

How far Covid vaccines can protect those who receive organ transplantations; data on this aspect is still scarce. Transplant physicians have long worried that the patients on transplantations may not be getting as much protection as they need from the Covid vaccines. One prominent feature has been that the transplant patients are not able to produce antibodies against the coronavirus even after being fully vaccinated with mRNA vaccines, which are thought to be the most effective ones, few studies have hinted.

A study recently published in the journal Transplantation has shown that the lack of antibodies in transplant patients, who have been vaccinated fully, is driving them towards a much higher risk of breakthrough COVID-19 cases. The breakthrough cases are those where fully vaccinated people get infected at least 14 days after the last dose of a vaccine. The study was corresponded by Dorry Segev, a transplant surgeon at the Department of Surgery, Johns Hopkins University School of Medicine, United States, and his colleagues.

In case of transplant patients, immuno-suppressant drugs are commonly used. The immune system (defence mechanism of the body) response is kept low with these drugs so that the body can be kept from rejecting a new organ. The suppression of the immune system puts the transplant patients at high vulnerability to the viral infection.

In a previous study co-authored by Dorry Segev, published in JAMA in May 2021, it was found that among 658 transplant recipients, only 54% of those receiving two doses of an mRNA vaccine could develop antibodies that were necessary to protect against the coronavirus. According to Dorry Segev, “Low antibody levels is a warning signal, but it does not necessarily mean that they have suboptimal protection.”

In the latest study published in Transplantation, Dorry Segev and his colleagues attempted to measure the protection provided by vaccines to transplant patients. The team of researchers obtained the coronavirus infection and testing data of about 18,000 people who received large organs like kidney or lungs transplanted. Those were also fully vaccinated with an mRNA vaccine against Covid. The team gathered the data from 17 transplant centres across the United States.

The research team found that among those studied, 151 were infected by the coronavirus. Again, out of those infected patients, more than half had to be hospitalised due to severe symptoms of COVID-19. Worryingly, the death rate was much higher among them--one in every ten patients died, pointing to a death rate of about 10%.

The rate of infection in the study may appear to be lower at 0.83% (151 infected out of 18000 patients studied), but it is staggeringly high when compared to the general public who are fully vaccinated. The study found that the rate of serious illness among the transplant patients were also alarmingly high--it was found to be 485 times higher in comparison to the general public.

However, the data in the study has received apprehensions from other experts. Eva Schrezenmeier, a nephrologist at Charité University Hospital, Berlin, said in a statement to Science magazine that the study might have actually underestimated breakthrough cases. The study might have missed some patients owing to the fact that patients may have gone to different hospitals for COVID-19 treatment or some may not have reported their breakthrough cases.

Another transplant infectious disease physician at University Health Network, Toronto, Deepali Kumar expressed similar views. She commented that she would like to know more about those who had breakthrough infections before drawing any conclusions. “Because the study is based on summary data and not complete medical records, it can’t provide information about whether the serious breakthrough cases were in older organ recipients, or in patients who received a particular kind of transplant. There are a lot of questions remaining,” she said further.

Can a Third Dose be a Solution?

Studies are under way to see whether a third dose (booster dose) can provide better protection for the transplant patients.

In a recent study published in NEJM (New England Journal of Medicine), it was found that when a third dose of the Pfizer vaccine (mRNA Vaccine) is administered in the transplant patients, 68% of them could produce antibodies in comparison to 40% of the vaccine recipients that received two doses of the vaccine.

In another study published in JAMA on July 23, doctors gave a third dose of the Moderna vaccine (mRNA Vaccine) to 159 patients who received kidney transplantation. These patients could produce very little or no antibodies when two doses of the vaccine were administered. But, after the third dose, 49% of the patients started to produce significant antibodies.

However, administering the third dose of any vaccine has not been recommended anywhere in the world yet. There need to be further studies before going for such approvals.