In hemodialysis, third dose of Pfizer vaccine may improve humoral response to COVID-19
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Administration of a third dose of the Pfizer-BioNTech COVID-19 vaccine boosted the humoral response to SARS-CoV-2 in patients on maintenance hemodialysis, according to a study in Clinical Kidney Journal.
“In April 2021 the French authorities recommended a third dose of SARS-CoV-2 mRNA vaccine in patients on renal replacement therapy,” Marine Dekervel, of the nephrology, dialysis and transplantation department at CHU Angers, France, and colleagues wrote. “At the time of the present report, France is the only country in which such a choice has been made. While this policy has a clear rationale, and the follow-up time is too short to allow an analysis of the efficacy on the risk of developing the disease, timing is crucial in the fight against COVID-19 and we considered that data on the effect of the third vaccine dose could be helpful in defining further vaccination strategies.”
Thus, Dekervel and colleagues assessed data of patients at three hemodialysis centers in France who received a third BNT162b2 (Pfizer-BioNTech) dose. The first two centers included 66 patients with any level of response to the second dose in its data (systematic cohort), while the other center included 34 patients with no or low response to the second dose in its data (conditional cohort).
Participants received their second Pfizer-BioNTech dose between February and April 2021, and their third dose at least 1 month after that date. Researchers compared anti-Spike immunoglobulin G (anti-S IgG) antibody concentrations following both the second and third doses.
In the systematic cohort, participants had an average anti-S IgG concentration of 1,056 UI/mL after the second dose and a concentration of 6,464 UI/mL after the third.
“Indeed, after the [third] dose, the median anti-S IgG titer was in the same range than that reported for healthy subjects who received a conventional vaccine schedule with the same assay,” Dekervel and colleagues wrote.
The percentage of participants with antibody response increased between the second and third dose from 83.3% to 92.4%. Of 11 participants who had not responded to the second dose, six (54.5%) became low responders. Twenty (95.2%) of the 21 low-responding participants become highly responsive.
In the conditional cohort, a similar trend occurred: The average anti-S IgG concentration increased from 17.8 U/mL to 1,180 U/mL between the second and third doses, with four of five non-responders developing significant anti-S IgG antibody concentrations. Within the cohort, 33 patients (97.1%) had improved response.
Limitations included small sample size, observational study nature, minimal follow-up, non-analysis of cellular response and use of different tests in the cohorts to analyze antibodies.
“The best way to prescribe the third vaccine dose is not established, and both a systematic approach, re-vaccinating all patients accepting it, and a conditional one in which vaccination is proposed in case with low response or when antibody titers decrease, are reasonable and feasible,” the researchers wrote.
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