GlaxoSmithKline (GSK) and South Korean pharmaceutical firm SK Bioscience have started a Phase 3 trial of their Covid-19 vaccine combination.

GSK told the stock market on Tuesday that the advance follows “positive” interim results in the Phase 1 and 2 studies.

It said the partners are now aiming for global supply through the Covax facility in the first half of 2022, subject to data and regulatory reviews.

However, latest figures show that around 88% of over-16s in the UK have already received at least one vaccine dose.

Thomas Breuer, chief global health officer, GSK, said, “While many countries have made good progress with vaccination, there remains a need for accessible and affordable Covid-19 vaccines to ensure equitable access and to protect people across the world.

“We are pleased to contribute with GSK’s pandemic adjuvant and to be working with SK to deliver the vaccine at scale via Covax if it is approved.”

The late-stage trial will enrol around 4,000 participants from a range of countries to evaluate the vaccine candidate’s safety and immunogenicity compared with the Oxford/AstraZeneca vaccine.

GSK said the study will be one of the first global late-stage trials to compare two different vaccine candidates.

SK Bioscience chief executive Jaeyong Ahn said: “We are grateful that we were able to advance to the Phase 3 study with the unprecedented support of global initiatives, including GSK, Coalition for Epidemic Preparedness Initiative, and the Bill & Melinda Gates Foundation.

“Taking this important step towards overcoming the global pandemic situation, SK and GSK will bring our technical expertise together for the development of an adjuvanted protein-based vaccine candidate, GBP510.”