A small study provides the first indication that an additional dose of COVID-19 vaccines
may provide some organ transplant recipients with an extra layer of protection.
Even as most vaccinated people
rejoice at their return to near-normalcy, millions of people who take immune-suppressing medications as a result of transplants, cancer
, or other disorders remain in limbo, unsure how well they are protected. It is simply more difficult for vaccines to activate a weak immune system.
Although the study on Monday only included 30 transplant patients, it is an important step toward determining whether booster doses could be beneficial.
It didn't help everyone, but of the 24 patients who appeared to have no protection after the routine two vaccinations
, eight — a third — developed some virus-fighting antibodies after an extra shot, researchers from Johns Hopkins University
reported in Annals of Internal Medicine. And six others who had only minimal antibodies all received a significant boost from the third dose.
“It’s very encouraging,” said Dr. Dorry Segev, a transplant surgeon at Johns Hopkins who helped lead the study. “Just because you’re fully negative after two doses doesn’t mean there’s no hope.”
Next, Segev's team hopes to begin a more rigorous test of a third vaccination in 200 transplant recipients this summer, in collaboration with the National Institutes of Health
For transplant patients, powerful immune-suppressing drugs prevent rejection of their new organs but also make them extremely vulnerable to the coronavirus
; they were excluded from initial testing of the COVID-19 vaccines, but doctors advise them to get vaccinated in the hope of at least some protection.
Some do benefit; the Hopkins team recently tested over 650 transplant recipients and discovered that 54% had virus-fighting antibodies after two doses of the Pfizer
vaccines — albeit at a lower rate than in otherwise healthy vaccinated people.
It's not just a concern after organ transplants, according to Dr. Alfred Kim of Washington
University in St. Louis
, who found that 85% of patients with rheumatoid arthritis, lupus, and other autoimmune disorders developed antibodies. However, those who used certain immune-suppressing drugs produced significantly lower levels, which is cause for concern.
“We tell our patients to act as if the vaccine isn’t going to work
as well as it does for their family and friends
,” said Kim, who would also like to test a third dose in autoimmune patients because “this is very frustrating news
People with weakened immune systems may receive additional doses of other vaccines, such as the hepatitis B vaccine.
In addition, Segev noted that guidelines issued in France
recommend a third COVID-19 shot for people with severely compromised immune systems, such as transplant recipients.
Although the United States
has not authorized additional COVID-19 vaccinations, a growing number of immune-compromised patients across the country are seeking third doses on their own — the people Hopkins sought to test.
, 48, of San Francisco
, agreed to blood tests before and after an additional dose after learning she had no measurable antibodies despite two Pfizer shots.
“I had gotten what I needed in order to survive,” Ladd said of the additional dose, but she is still wearing masks
and taking other precautions.
“I’m being as cautious as I can while also acknowledging that I’m returning to the world of the living,” she explained.
More research is needed to determine whether a third dose is truly beneficial, who is the best candidate, and whether brand differences exist — as well as whether the extra immune stimulation increases the risk of organ rejection.
But, as Segev points out, boosters aren't the only option. Vaccinations, in addition to antibodies, normally stimulate T cells, which can protect against severe illness. He and several other research groups are investigating whether immune-compromised patients benefit from this benefit.
For the time being, “the best way to protect these people is for others to get vaccinated,” so they are less likely to be exposed to the coronavirus, according to Kim of Washington University.
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