Humoral immune response against SARS-CoV-2 after adapted COVID-19 vaccine schedules in healthy adults: The IMCOVAS randomized clinical trial

Jul 17, 2024Vaccine

Antibody response to COVID-19 after different vaccine schedules in healthy adults

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Abstract

Prolonging the interval between vaccinations from 28 to 84 days and using a heterologous vaccination schedule resulted in a non-inferior immune response.

A low dose of mRNA-1273 was found to induce non-inferior immunity compared to standard doses.
Non-inferiority for intradermal vaccination could not be demonstrated.
Anti-Receptor-Binding Domain immunoglobulin G (RBD IgG) titres after a first booster were non-inferior across all adapted vaccination schedules.
The findings indicate that vaccine schedules can be modified without compromising immune response.
Immunity following a booster did not depend on the dose or brand of the booster vaccine.

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BACKGROUND: To overcome supply issues of COVID-19 vaccines, this partially single blind, multi-centric, vaccine trial aimed to evaluate humoral immunogenicity using lower vaccine doses, intradermal vaccination, and heterologous vaccine schedules. Also, the immunity after a booster vaccination was assessed.

METHODOLOGY: 566 COVID-19-naïve healthy adults were randomized to 1 of 8 treatment arms consisting of combinations of BNT162b2, mRNA-1273, and ChAdOx1-S. Anti-Receptor-Binding Domain immunoglobulin G (RBD IgG) titers, neutralizing antibody titres, and avidity of the anti-RBD IgGs was assessed up to 1 year after study start.

RESULTS: Prolonging the interval between vaccinations from 28 to 84 days and the use of a heterologous BNT162b2 + mRNA-1273 vaccination schedule led to a non-inferior immune response, compared to the reference schedule. A low dose of mRNA-1273 was sufficient to induce non-inferior immunity. Non-inferiority could not be demonstrated for intradermal vaccination. For all adapted vaccination schedules, anti-RBD IgG titres measured after a first booster vaccination were non-inferior to their reference schedule.

CONCLUSION: This study suggests that reference vaccine schedules can be adapted without jeopardizing the development of an adequate immune response. Immunity after a booster vaccination did not depend on the dose or brand of the booster vaccine, which is relevant for future booster campaigns. The trial is registered in the European Union Clinical Trials Register (number 2021-001993-52) and on clinicaltrials.gov (NCT06189040).

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Humoral immune response against SARS-CoV-2 after adapted COVID-19 vaccine schedules in healthy adults: The IMCOVAS randomized clinical trial

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