Vaccine development is a complex process, traditionally it takes as long as 20 years, said Ashish Pal, vice-president of the Singapore Association of Pharmaceutical Industries (SAPI).

"You have pre-discovery phase that can last two to four years. Pre-clinical and clinical trials can take anything between five and 15 years and that does not include regulatory approvals and manufacturing," Channel News Asia reported on Monday quoting Pal.

In the last nine months since the COVID-19 outbreak, around 170 vaccine candidates have shown promise, with 26 of them entering the human trial stage, according to the World Health Organization (WHO), which cautions against haste.

"Companies that are developing vaccine candidates are now working on multiple elements of the development process, - so (it) is in many ways much more risky, given the fact that a lot is happening much faster, and also in tandem," said Pal, who is also the managing director of MSD Pharma Singapore.

"More than ever, there is need for urgency but most importantly, without compromising on safety," he told the channel.

Pal said the people could take a great amount of comfort from the joint pledge made by nine American and European vaccine developers.

Pfizer, GlaxoSmithKline, AstraZeneca, Johnson & Johnson, Merck & Co, Moderna, Novavax, Sanofi and BioNTech, in a joint statement, has said they would "uphold the integrity of the scientific process as they work towards potential global regulatory filings and approvals of the first COVID-19 vaccines".

"Obviously there''s a lot out there about timeframes but the whole process as I''ve outlined is complex. It''s probably too early at this point in time to speculate when a vaccine candidate would be approved," he said.

A vaccine has long been awaited to immunise the world against the novel coronavirus that has claimed over 900,000 lives across the world so far.

Earlier this month, the WHO said it does not expect widespread vaccinations against COVID-19 until the middle of next year. None of the candidate vaccines in advanced clinical trials have demonstrated a "clear signal" of efficacy at the level of at least 50 per cent, the WHO had said.

The challenges could be seen when a potential vaccine being developed by British drug maker AstraZeneca and Oxford University hit the pause button last week, following an unexplained illness in a study participant.

The WHO's chief scientist had called the pause a "wake-up call", urging researchers not to be discouraged.

The challenges do not end at development of a vaccine. Manufacturing and distribution will be key areas where global cooperation will be required, Pal said.

Given how manufacturing will likely have to be done at "an unprecedented scale", he said, "Companies are probably using a variety of options from expanding manufacturing sites to either refitting or re-purposing their global networks, and identifying additional opportunities to supplement their networks."

Asked about industry collaboration given the lucrative option of a successful vaccine, Pal said, "We are already seeing many examples of industry and academia, as well as industry and industry coming together so I think there are already some very real examples of unique and relevant collaboration today."

Distribution of the vaccines will be based on "an equitable distribution that is agnostic to economic tiers", said the SAPI vice-president.

This is being followed by COVID-19 Vaccine Global Access (COVAX) facility, a global allocation plan led by the WHO, the GAVI vaccine alliance and the Coalition for Epidemic Preparedness Innovations, he added.

Launched in late April, the COVAX facility works with vaccine manufacturers to provide countries worldwide with "equitable access to safe and effective vaccines", said the WHO. It aims to deliver at least 2 billion doses of approved vaccines by the end of 2021.

For now, it relies on nine experimental vaccines that are across various stages of development and employ a range of different technologies and scientific approaches.

On whether the emerging trend of "vaccine nationalism" could impede the effectiveness of the COVAX facility, Pal said, "I think what countries choose to do is obviously an individual choice. COVAX is a very important platform at this time more than ever before (because) its intent is in line with how best the world can navigate this global pandemic."

Pal stressed that Singapore plays an important role in the global bio-pharmaceutical industry.

He pointed to how the industry, which employs more than 24,000 people, remains a bright spot for the Singapore economy despite the current pandemic-fuelled downturn.

"We have companies that have significant manufacturing and research and development (R&D) presence in Singapore. The range of manufacturing and R&D is varied and what each company is choosing to do is obviously company proprietary," said Pal.