Nations across the world are doing their best to ramp up the inoculation of their populations against COVID-19, with a special focus on high-risk sections. Nearly all these groups are believed to be sufficiently protected by the vaccines. Nevertheless, a new study states that organ transplant recipients—who are at an increased risk due to their immunocompromised state—are vulnerable to SARS-CoV-2 even after receiving the second dose of vaccination.

According to the study by researchers from Johns Hopkins Medicine, which is a follow-up to an earlier study of theirs, two doses of COVID-19 vaccines provide some amount of protection (54 percent overall) to solid organ transplant patients. However, it is not adequate enough for them to ease up on crucial safety measures such as physical distancing, and wearing of masks, among others.

"Based on our findings, we recommend that transplant recipients and other immunocompromised patients continue to practice strict COVID-19 safety precautions, even after vaccination," emphasized Dr. Brian Boyarsky, lead author of the study, in a statement.

Insufficient Antibody Levels 

Lungs (Representational Picture)Pixabay

When individuals receive solid organ transplants such as kidneys, heart, and lungs, they are often prescribed medication for the suppression of their immune system. This is done in order to ensure that their body does not reject the received organ. However, such treatments can affect the ability of the transplant recipient's body in making antibodies against foreign substances. Unfortunately, it also includes protective ones generated as a response to vaccines.

In their earlier study published in March 2021, the researchers evaluated the antibody-producing capacity in participants who were organ transplant receivers. They had received the first dose of one of the two mRNA vaccines— Moderna and Pfizer-BioNTech —against COVID-19. Disappointingly, only 17 percent of the participants produced enough antibodies after receiving one dose of the two-dose course of COVID-19 vaccines.

Evaluating Effects of Second Dose

For the current study, the authors investigated the immunogenic response in 658 transplant recipients after they received the second dose of either of the vaccines. None of the participants had been diagnosed with COVID-19 previously and completed the two-dose regimen between 16 December 2020 and 13 March 2021. 

COVID Vaccine
COVID-19 vaccine (Representational Picture)Pixabay

The scientists learned that only 98 of the 658 participants (15 percent), had antibodies that were detectable 21 days after receiving the first dose of the vaccines. These results were nearly similar to the one obtained in their previous study (17 percent).

Twenty-nine days after receiving the second dose, the number of participants with identifiable antibodies increased to 357 out of 658 (54 percent). Following the administration of both doses, 301 out of 658 participants (46 percent) possessed no detectable antibodies at all. 259 participants produced antibodies only after receiving their second dose.

"While there was an increase in those with detectable antibodies–54 percent overall–after the second shot, the number of transplant recipients in our second study whose antibody levels reached high enough levels to ward off a SARS-CoV-2 infection was still well below what's typically seen in people with healthy immune systems," noted Dr. Boyarsky.

Need for Caution 

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SARS-CoV-2 (Representational Picture)Pixabay

Additionally, the team also discovered that among the participating patients, the ones that had a higher likeliness of developing an antibody were those who were younger, were not on immunosuppressive medications (including anti-metabolite drugs), and had been administered the Moderna vaccine. These findings were similar to the link witnessed in the single-dose study published in March.

"Given these observations, transplant recipients should not assume that two vaccine doses guarantee sufficient immunity against SARS-CoV-2 any more than it did after just one dose," highlighted Dr. Dorry Segev, co-author of the study.

Dr. Segev called for future studies that focus on improving the response of COVID-19 vaccines in solid organ transplant receivers. They must also include the adjusting of immunosuppressive treatments or more booster shots in order to ensure that sufficient levels of antibodies are produced in this population, he concluded.