May 11, 2021


The mRNA vaccines of Pfizer-BioNTech and Moderna have proved to be highly successful in preventing COVID-19 infection and saving lives around the world, including Israel, where life has returned almost to normal.

But a new study just concluded at Tel Aviv Sourasky Medical Center has shown there is one exception: The effectiveness of the coronavirus vaccine among organ-transplant recipients is significantly lower than in the general population.

The study, conducted at the hospital’s transplant clinic, examined the response to the vaccine in liver and kidney transplant by measuring the levels of neutralizing antibodies to the virus that develop as a result of the vaccine. The study included 136 kidney transplant recipients and 80 liver transplant recipients. 

After receiving the vaccine, all participants in the control group developed antibodies at a normal level of around 95% or more, while among the transplant recipients the vaccine effectiveness was significantly lower. Only 47.5% of liver transplant recipients developed antibodies, and among kidney transplant recipients even less – just 37.5% developed antibodies. 

The reduced effectiveness of the vaccine was also related to age, kidney function and the type of anti-rejection drugs the patients received. In addition, the levels of antibodies developed by the transplant recipients were found to be significantly lower relative to the control group. But the authors – Dr. Liane Rabinowich, Dr. Ayelet Grupper and Dr. Helena Katchman of the transplant clinic – stressed that the vaccines are safe and did not cause side effects or rejection of the transplanted organs.

Left to right: Dr. Liane Rabinowich, Dr. Ayelet Grupper and Dr. Helena Katchman
Credit to Tel Aviv Sourasky Medical Center

The study, published in the American Journal of Transplantation under the title “Reduced humoral response to mRNA SARS-Cov-2 BNT162b2 vaccine in kidney transplant recipients without prior exposure to the virus,” has an important message for organ-transplant recipients and their physicians – that they can’t rely on the mRNA vaccines to protect against coronavirus infection and they must continue to observe the precautionary rules of masks, social distancing and hygiene. 

In addition, they wrote, “we do not yet know what the effectiveness of the vaccine is in reducing severe morbidity [disease] and infection and how long the antibody level will remain positive. These days, the research group is working on further research that will help answer these questions. We hope our research will also help find a way to increase the effectiveness of the vaccine in transplant recipients.”