Some Kidney Transplant Patients Respond to Fourth COVID Vax Dose

A fourth dose of mRNA COVID-19 vaccine boosted antibodies among half of kidney transplant recipients with suboptimal immune responses after three doses, a French case series found.

Among 92 patients with low anti-spike IgG titers (below 143 binding antibody units/mL) 1 month after the third dose, 50% reached the 143 BAU/mL threshold considered adequate against the initial COVID variants at 1 month following their fourth dose, reported Sophie Caillard, MD, PhD, of Hôpitaux Universitaires de Strasbourg in France, and colleagues.

Moreover, only one patient out of the group who still had an extremely suboptimal response (28 BAU/mL) at 1 month after the fourth dose went on to develop “mild” COVID-19, the authors wrote in Annals of Internal Medicine.

CDC recommended in October that “moderately or severely immunocompromised people,” including solid organ transplant recipients, receive a fourth dose of COVID-19 vaccine. Interestingly, another French study in a smaller cohort of organ transplant recipients reported in November that this population exhibited suboptimal immune responses, even after four doses of Pfizer vaccine.

Caillard’s group noted that anti-spike IgG titers above 143 BAU/mL “correlate with the presence of neutralizing antibodies” against the wild-type, Alpha, Beta and Gamma variants, but not Delta, which “requires higher [anti-spike] IgG titers.”

After the French government approved a fourth dose of vaccine for solid organ transplant recipients, the authors examined a group of kidney transplant recipients who had a suboptimal vaccination response 1 month after their third dose and received a fourth dose.

Median age of these patients was 56, about 70% were men and 83% had hypertension. They had a median of 68 days between their third and fourth dose. There were 34 patients who received Pfizer’s vaccine, while 58 received Moderna’s.

Caillard’s group reported no safety concerns with the fourth dose, which increased median anti-spike IgG from 16.4 to 145 BAU/mL. Overall, 48% of patients who received a fourth dose of Pfizer and 52% of patients who received a fourth dose of Moderna recorded IgG titers above 143 BAU/mL. Patients receiving Moderna had higher median IgG titers than those receiving Pfizer (150 vs 122, respectively).

The researchers noted certain limitations to the data, such as the fact that they did not examine T-cell immunity following vaccination in this population, and that an increase in anti-spike IgG titers does not “invariably provide protection against infection and disease.”

Caillard’s team suggested offering a prophylactic dose of monoclonal antibodies to patients who could not produce an adequate immune response to additional vaccine doses.

Last Updated January 10, 2022