Health Matters spoke with Dr. Pereira to understand who is currently eligible for an additional vaccine shot, why, and what we can expect in the near future.
Why did the FDA and CDC decide that immunocompromised individuals could use a third shot?
The background to this decision is that a number of studies in immunocompromised patients, including solid organ and stem cell transplant patients, and those with hematological malignancies and cancer, all consistently mounted a weaker immune response after the vaccine when compared to the general population.
In kidney transplant recipients, for example, a study performed here at NewYork-Presbyterian/Columbia University Irving Medical Center showed that only about 40% of patients formed antibodies after full COVID vaccination, as compared to over 90% for the general population. Another study from Johns Hopkins looked at over 1,000 patients and saw the same results — these patients had low antibody formation. Studies in Germany and France all showed a very reduced response to the vaccine compared to the general population.
Throughout the spring, we were seeing lower rates of infections throughout the United States and not a lot of breakthrough infections. Unfortunately, with the Delta variant, that has changed. So that concern about the potential for breakthrough infections combined with a number of studies culminated in this newer recommendation of providing an additional dose to those immunocompromised patients who have been fully vaccinated.
Why do immunocompromised people benefit from an extra shot?
We have known historically from prior vaccines, including influenza and the pneumonia vaccines, that immunocompromised patients generally have a weaker response to vaccines. This is not unique to the COVID vaccines. The reason for that is because vaccines require a functioning immune system to work efficiently.
The vaccine is essentially a set of instructions to your immune system that say, “Here, recognize this signal. If you ever see it in the future, respond very fast to it. Learn from this injection.” For your body to learn from that injection and to carry out that set of instructions, you need a functioning immune system. But when transplant patients, for example, receive a vaccine, that response is much reduced, unfortunately. And we’ve known from research with influenza, pneumonia, and hepatitis B vaccines that additional doses are required to match or even come close to a vaccine response in someone who is not immunocompromised.
When your immune system is weak and not functioning as it should, this can lead to a greater risk of infection and illness. We need the production of antibodies (proteins that identify pathogens in the body) and T cells (white blood cells that work with antibodies) to identify and elicit an immune response to fight off infection. An additional dose of vaccine may improve immunocompromised people’s immune response and help further protect them from severe disease.
Who is eligible to receive a third dose?
Immunocompromised could be an incredibly broad category, and some people may not squarely fit in it. The ones who would be clearly included would be solid organ transplant recipients, stem cell transplant recipients, those actively being treated for a malignancy with chemotherapy, and patients who were born with a weaker immune system. Also, those with advanced or untreated HIV infection, including those with T cells less than 200, and patients who are taking high-dose corticosteroids, which is equivalent to about 20 milligrams of prednisone per day, or taking other agents for their autoimmune diseases.
Is there research on how the additional shot has performed for this population?
Yes, a number of studies show that third shots benefit people with a suppressed immune system. Studies from France, Israel, and Canada, among others, all showed that in solid organ transplant recipients, immune responses went from about 40% after the second dose to almost 70% after the third dose. This showed that immunocompromised people benefitted from getting additional doses of these vaccines.
At NewYork-Presbyterian/Columbia University Irving Medical Center, we are studying how the immunocompromised population responds to third doses and anticipate more studies to investigate vaccine responses.