The COVID-19 vaccine being developed by Britain's GlaxoSmithKline and France's Sanofi won't be ready until late 2021 as they seek to improve the immune response in older adults, the companies announced on Friday.
The companies said in a statement that "insufficient response in older adults demonstrates the need to refine concentration of antigen in order to provide high-level response across all age groups."
Interim results from Phase 1 and 2 trials showed that for adults aged 18-49 years, the immune response triggered by their vaccine candidate is comparable to patients who have recovered from COVID-19.
Another study conducted in non-human primates also showed that the vaccine could protect against lung pathology and lead to rapid viral clearance from the nasal passages and lungs within two to four days.
Roger Connor, President of GSK Vaccines conceded that "the results of the study are not as we hoped."
Thomas Triomphe, Executive Vice President and Head of Sanofi Pasteur, added that they "have identified the path forward and remain confident and committed to bringing safe and efficacious COVID-19 vaccine.
"Following these results and the latest encouraging new preclinical data, we will now work to further optimise our candidate to achieve this goal," he added.
The companies now plan to start a Phase 2b trial in February 2021 and if data if positive, start Phase 3 — when the vaccine is tested on thousands of people to test its safety and efficacy — in the second quarter of next year.
"Positive results from this study would lead to regulatory submissions in the second half of 2021, hence delaying the vaccine's potential availability from mid-2021 to Q4 2021," the statement said.
So far, China, Russia and the UK have started mass vaccination campaigns. The first two countries use their own developed vaccines while the UK was the first to roll out the vaccine developed by Pfizer, an American company, and Germany's BioNTech.
The Pfizer/BioNtech vaccine has been found to be more than 90 per cent effective in preventing the disease.
It has also been approved by regulators in Canada while the US's Federal Food and Drugs Administration and the European Medicines Agency have both started the authorisation process.