Dr. Poland, Mayo Clinic infectious diseases expert addresses the question of a booster shot and organ transplant recipients in the latest Q&A podcast here:
- Summer travel and people not in your bubble during COVID-19 pandemic https://connect.mayoclinic.org/blog/podcasts/newsfeed-post/poland-2/

Start at 16:00 minutes.
From the transcript:
“So, let's take the case of solid organ transplant patients. They're among the most immunosuppressed. So, how do we protect them? Well, the studies have shown and I'm going to simplify because there are a number of studies. But after one dose, you maybe get protection in the low teens. After two doses about 30 to 40% of transplant patients can be protected. After three doses, and I'm talking about mRNA vaccines now, they've been able to demonstrate protection up to about the 70% level. So, I was on a phone call last week with senior decision makers in the US about this. And you know, we talked very freely about the fact that we need more data. We are keeping an eye on these variants. It is likely to be the variants over anything else that might push us toward a booster. So, again, we're seeing an effect we need never have worried about had we been able to get people to wear masks and get vaccines. So, I think we'll first see recommendations in people who are highly immunosuppressed. I think it's very much an open question at this point as to whether otherwise healthy people will need vaccines, possibly we'll see a recommendation in the elderly. But again, we don't have a full measure of what's called a correlative protection. And even those correlates of protection, for the most part, ignore cellular immunity, which is an arm equally as important as antibody. So, a lot of work and research to be done. I think where we'll make that decision is if we start seeing breakthrough infections occur at greater rates over time in certain subpopulations, like organ transplants or immunosuppressed, or the elderly. But at this point, I think we're doing the right thing and preparing for the idea, but I think any recommendation at this point would be premature.“