Stas K, Kuypers D. MO882: Heterologous versus Homologous Triple Anti-Covid-19 Vaccine Regimens in Patients on Maintenance Hemodialysis

BACKGROUND AND AIMS

Vaccination against COVID-19 is a promising strategy to reduce the risk for severe COVID-19. Patients on maintenance haemodialysis have a less robust immunoresponse than the general population. Triple vaccination might improve immunogenicity, and might benefit patients having a poor initial response. The aim of the current study was to evaluate the humoral response to heterologous (a combination of different vaccine types) versus homologous (three identical vaccines) triple vaccination against COVID-19.

METHOD

We analyzed serological response to homologous (3 times mRNA-based vaccine) versus heterologous (adenoviral vectored plus mRNA vaccines) triple regimens in samples from patients on maintenance dialysis (NCT04378686). We measured IgG anti–S (spike) SARS-CoV-2 antibody levels using the IgG II Quant assay (Abbott). Samples were collected between 6 and 12 weeks after both the second and the third vaccine dose.

RESULTS

A total of 302 patients received three vaccine doses. 94 patients received a heterologous regimen of the adenoviral vectored AZD1222 (2 doses) and the mRNA-based BNT162b2 (1 dose). The remaining 208 patients received a triple mRNA vaccine regimen of either BNT162b2 (n = 149) or mRNA-1273 (n = 59). Triple vaccine regimens resulted in significant elevation of anti-S titers, as compared with the conventional prime-boost (double) vaccination. A substantially and significantly larger fraction of patients reached the threshold for neutralizing antibodies after triple vaccination, as compared with after double vaccination. The yield of a third dose of mRNA-1273 is less than the yield of a third dose of BNT162b2. This, however, mainly reflects the initial significant better response to mRNA-1273. In multivariate analysis, a past episode of COVID-19 was a strong modulator of the response after double vaccination, and after triple vaccination.

CONCLUSION

Both heterologous and homologous triple vaccine regimens significantly augment the humoral response against SARS-CoV-2. The higher the ininitial response to the double prime-boost regimen, the lower the yield of a third vaccine dose. It seems prudent to prioritize vaccination of dialysis patients using mRNA-based vaccines when available.

A False-Positive Gamma-Hydroxy Butyric Acid Urine Screening in a Patient with High Anion Gap Metabolic Acidosis Due to Ethylene Glycol Poisoning

A young woman with a history of several suicide attempts was admitted to the hospital after suspicion of a new intoxication without definite identification of the causing agent. The patient had a high anion gap metabolic acidosis (HAGMA) with respiratory compensation, a lactate gap and an osmolar gap at admission. Initial toxicological screening showed no abnormalities except for a weak positive gamma-hydroxy butyric acid (GHB) enzymatic screen in urine. This finding could not be confirmed using chromatographic analysis nor be explained by the presence of known cross-reacting substances like ethanol. In this case, falsely elevated urinary GHB screening was caused by the ingestion of ethylene glycol. To confirm that the interference was due to ethylene glycol or its metabolites, we performed a spiking experiment. Cross reactivity was linked to ethylene glycol and was low in our experiments (0.1-0.2%). Substantial amounts of ethylene glycol are required to slightly elevated GHB results, depending on the endogenous cutoff used. We can conclude that ethylene glycol can give rise to falsely elevated urinary GHB levels at ethylene glycol concentrations that are typically found in intoxications.