Booster Immunisation with Skin-Patch-Delivered Unadjuvanted SARS-CoV-2 Spike Protein Vaccine Is Safe and Immunogenic in Healthy Adults

Christopher L.D. McMillan; David A. Muller; Germain J.P. Fernando; Alexandra C.I. Depelsenaire; Cesar Jayashi-Flores; Kelly Anne Masterman; Sarika Namjoshi; Kartik Vyas; Deborah Pascoe; Julian Hickling; Stephanie Wallace; Daniel Duijsings; Joelle Vink; Adam K. Wheatley; Jennifer Juno; Greg Siller; Angus H. Forster

doi:10.3390/vaccines14010028

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Booster Immunisation with Skin-Patch-Delivered Unadjuvanted SARS-CoV-2 Spike Protein Vaccine Is Safe and Immunogenic in Healthy Adults

Journal article

Open access

Peer reviewed

Booster Immunisation with Skin-Patch-Delivered Unadjuvanted SARS-CoV-2 Spike Protein Vaccine Is Safe and Immunogenic in Healthy Adults

Christopher L.D. McMillan, David A. Muller, Germain J.P. Fernando, Alexandra C.I. Depelsenaire, Cesar Jayashi-Flores, Kelly Anne Masterman, Sarika Namjoshi, Kartik Vyas, Deborah Pascoe, Julian Hickling, …

Vaccines , Vol.14(1), pp.1-22

2026

DOI: https://doi.org/10.3390/vaccines14010028

PMID: 41600944

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Abstract

HexaPro

microarray patch

microneedles

phase 1 clinical trial

SARS-CoV-2

thermostable vaccine

Background/Objective: Despite available SARS-CoV-2 vaccines, coverage gaps persist due to unequal distribution and limited access. Microarray patches offer a promising solution to address these challenges, providing a safer and easier-to-use alternative. We present a randomised, double-blind Phase I clinical trial evaluating the SARS-CoV-2 spike protein subunit vaccine, HexaPro, delivered via a high-density microarray patch (HD-MAP). Methods: Forty-four healthy adults aged 18–50 years were assigned to receive either 0 µg, 15 µg, or 45 µg of HexaPro via the HD-MAP, with the primary objective of assessing safety and tolerability. Results: The HD-MAP HexaPro vaccine was found to be safe and well tolerated, with only mild adverse events reported. Following vaccination significant increases in spike-specific IgG titers were observed by 7 days and remained stable through day 90. This IgG response effectively neutralised multiple SARS-CoV-2 variants. Additionally, the HexaPro HD-MAP was stable for up to 12 months at 40 °C. Conclusions: These findings support the continued clinical development of HD-MAPs as an alternative vaccination strategy.

Details

Title: Booster Immunisation with Skin-Patch-Delivered Unadjuvanted SARS-CoV-2 Spike Protein Vaccine Is Safe and Immunogenic in Healthy Adults
Authors: Christopher L.D. McMillan - The University of Queensland
David A. Muller (Corresponding Author) - The University of Queensland
Germain J.P. Fernando - The University of Queensland
Alexandra C.I. Depelsenaire - The University of Queensland
Cesar Jayashi-Flores - Vaxxas (Australia)
Kelly Anne Masterman - Vaxxas (Australia)
Sarika Namjoshi - Vaxxas (Australia)
Kartik Vyas - Vaxxas (Australia)
Deborah Pascoe - Vaxxas (Australia)
Julian Hickling - Working in Tandem Ltd (United Kingdom)
Stephanie Wallace - University of the Sunshine Coast
Daniel Duijsings - Cerba Research (Netherlands)
Joelle Vink - Cerba Research (Netherlands)
Adam K. Wheatley - The University of Melbourne
Jennifer Juno - The University of Melbourne
Greg Siller - The University of Queensland
Angus H. Forster (Corresponding Author) - Vaxxas (Australia)
Publication details: Vaccines , Vol.14(1), pp.1-22
Publisher: MDPI AG
Date published: 2026
DOI: 10.3390/vaccines14010028
ISSN: 2076-393X
PMID: 41600944
Copyright note: © 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.
Data Availability: All data reported in this paper is available in this article.
Grant note: This research was entirely funded by Vaxxas Pty Ltd., Brisbane, Queensland 4007, Australia.
Organisation Unit: UniSC Clinical Trials Centre
Language: English
Record Identifier: 991214173302621
Output Type: Journal article

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