Response to a third SARS-CoV-2 vaccine dose amongst immunoco
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While the available COVID-19 vaccines have proven highly effective for most individuals, patients receiving immunosuppressive medication, such as those administered following an organ transplant, exhibit an inhibited immune response towards the vaccine, thus lowering their efficacy.

In an attempt to provide some level of immunity to these already high-risk patients, alternative vaccination schemes have been adopted, including the administration of a third dose. All 25 patients involved in the study had previously received the BioNTech mRNA vaccine within the proper dosing regimen: two doses, 21 days apart. Around half of the patients were then given either a third dose of the mRNA vaccine, on average 127 days after the first dose, or alternatively the AstraZeneca adenovirus vector-based vaccine, on average 90 days after the first vaccine.

All patients had failed to develop a sufficient anti-SARS-CoV-2 spike protein Immunoglobulin G (IgG) response before administration of the third vaccine, and all but one was presently receiving antimetabolite medication that has been demonstrated to diminish the immune response towards SARS-CoV-2.

SARS-CoV-2 specific IgG and IgA were determined at multiple time-points for each patient by enzyme-linked immunosorbent assay, with just three of the 25 developing detectable levels one week following administration of the third dose, though another nine showed evidence of seroconversion at later time points.

SARS-CoV-2 specific IgG levels were only significant amongst three patients: two having received the mRNA vaccine and one the adenovirus vector-based vaccine. Anti-spike protein IgA levels and virus-neutralizing capacity peaked around three weeks after receiving the third dose in the majority of participants.