How Do COVID-19 Vaccines Benefit Transplant Recipients?

A new commentary from experts highlight the evolving understanding of antibody response in vaccinated transplant patients.

A new editorial from an international team of investigators highlighted the still present uncertainties that surround organ transplant recipients’ response to COVID-19 vaccination.

The to-be-published perspective—penned by Emily A. Blumberg, MD, of the Perelman School of Medicine at the University of Pennsylvania, and colleagues from Chicago, Switzerland, and Germany—emphasized the difficulty to determine vaccine efficacy in the transplant population. Among the prevailing factors include a small count of transplant patients included in vaccine assessment, the emergence of SARS-CoV-2 variants, and greater COVID-19 precautionary measure adherence.

“Consequently, assessment of immunogenicity, including measurements of antibodies to the spike receptor-binding domain and evaluation of cellular responses, provides important information to define the host response to this vaccine,” they wrote.

Blumberg and colleagues highlighted a preliminary report of social media-enrolled trial participants who represented transplant recipients who received their first dose of an authorized mRNA vaccine for the prevention of COVID-19.

The outcomes of the large, diverse population showed SARS-CoV-2 spike antibody response in vaccinated transplant recipients via samples from standard venipuncture or novel home collection devices with 2 different marketed assays.

“After the first dose of the mRNA-based COVID-19 vaccine, the authors observed that less than 20% of patients had detectable antibodies, with the lowest response in those receiving antiproliferative medications and older individuals,” they wrote. “The impact of age has previously been noted in non-immunosuppressed individuals.”

Blumberg and colleagues added that investigators observed lesser antibody response to Pfizer-BioNTech’s BNT162b2 versus Moderna’s mRNA-1273. They identified no outstanding nor unexpected safety concerns. The findings are consistent with outcomes observed in transplant recipients to have received other vaccines including the seasonal influenza product.

“Nevertheless, although no real-world control group was recruited, the immunogenicity as measured by antibody response to mRNA COVID-19 vaccines in transplant recipients seems to be poor, especially when compared with the general population,” they wrote. “Similar results are now being reported from two other centers.”

While early outcomes are indicative of limited mRNA COVID-19 vaccine success within the transplant recipient community, discussion in possibly improving outcomes has focused on limiting therapeutic influence. As Blumberg and colleagues wrote, though these indications are preliminary, it has been enough for transplant community members to advocate for changes in in patient management leading up to COVID-19 vaccination, including suspending use of anti-proliferative agents.

“However, unproven alterations in immunosuppression may ultimately be more detrimental than beneficial if changes increase the risk of rejection or provide no meaningful improvement in vaccine responses,” they wrote.

Some other measures of product-dependent vaccine preferences for transplant recipients, emphasized second- and further booster-dosing of such patients, have been voiced.

But the experts’ takeaway from this developing understanding of COVID-19 vaccine antibody response in transplant recipients is that timing is key. They wrote it may be “preferable” to initiate vaccinations in wait-listed patients, in order to avoid immunosuppression-associated shortcomings in antibody response.

Even that suggestion, however, is limited by the lack of knowledge surrounding post-transplant protection as it relates to impact induction immunosuppression.

“Additionally, if a lower response to SARS-CoV-2 vaccines is confirmed, public health authorities and transplant providers will need to have different thresholds for when these patients may safely return to more normal activity,” they wrote. “Until we have more data, we should advocate continued adherence to diligent mask use, hand hygiene and social distancing.”