Singificantly, there were no serious or severe adverse effects and the antibody responses showed a dose-dependent trend.

The success of the patch could mean self-administration and would overcome the cost of refrigerating vaccines.

Chief executive David Hoey said the company was very encouraged by the compelling early data, which was released at a Boston biotech expo today.

“We believe our patch-based delivery of a next-generation spike protein has the potential to offer best-in-class protection against Covid-19 along with cost-effective distribution without the need for refrigeration,” he said.

Vaxxas is a spin-out from the University of Queensland. Its small patches, which look like a button, have about 5000 tiny projections that administer the vaccine.

The trial was done on 44 adults who had previously had three doses of the Covid vaccine, the last being four months before the study.

Vaxxas said the interim data supported its progress for seeking approval with the Therapeutic Goods Administration and the Food and Drug Administration in the US.

Two more trials were yet to be conducted but the company said the patch could be available by 2025. The first trial was conducted at the University of the Sunshine Coast.

The company raised $34 million in December to expand its manufacturing capabilities and also received an $8 million grant from the Federal Government in September.