iwCLL 2021 | The efficacy of COVID-19 vaccines in patients with CLL

COVID-19 has hugely impacted on our management of patients with CLL. And we have previously demonstrated in international retrospective series that actually the case fatality rate of patients with CLL hospitalized for severe COVID-19 infection is higher than expected in the general population. So, we of course rely on the efficacy of vaccination strategies. And so far, the vast majority of data presented are based on mRNA vaccines administered to patients with CLL, a different stage of the disease course. Some of them were treatment-naïve. Of course the relevant proportion were receiving treatment.

And what we can, let’s say, derive from the experience we have already gather is that patients with controlled disease of treatment are those who get the best response to vaccine for COVID-19. Followed by those who are watch-and-wait. But for patients on treatment the antibody titers, because actually it should be clarified that what we know so far is only the response in term of serological response, meaning that we are measuring the antibody titers in the peripheral blood, so, we know we have very few information on T-cells responses and memory B-cells persisting after vaccinations. But if we base our analysis on the levels of antibodies in the peripheral blood, what we have seen so far is that the serology titers is above the threshold only in a minority of patients receiving treatment. And in particular, the serological responses impaired in those who have recently received or are receiving anti-CD20 monoclonal antibodies.

So, there is an issue with the timing of vaccination. We should clarify the best timing for administering the vaccine doses. I just say the earlier, the better. Unless the patient is receiving anti-CD20 monoclonal antibodies. And then also there are preliminary evidences that the antibody titers obtain is lower than that obtained in the general population and is decreasing over time. So, there is still discussion and probably in the next future, we will have more data on the efficacy of additional shots of vaccination in patient with immune depression, including impaired immune function related to CLL.