CHICAGO, Jan 18 (Reuters) - Global health charities the Bill & Melinda Gates Foundation and Wellcome Trust each pledged $150 million to the Coalition for Epidemic Preparedness Innovations (CEPI) to fund its COVID-19 pandemic response and help put it on better footing for future major health crises.

The pledges, announced on Tuesday, come ahead of a March 8 fundraising event sponsored by the UK government that aims to raise $3.5 billion on behalf of CEPI, an international coalition set up five years ago to prepare for future disease threats.

CEPI's five-year strategy aims in part to compress vaccine development timelines to 100 days, around a third of the time it took the world to develop the first COVID-19 vaccines.

"The unprecedented spread of the highly infectious Omicron variant around the world over the past two months exemplifies the ways in which we must be ready both in terms of speed and the scale of our response to future threats," CEPI Chief Executive Richard Hatchett told reporters in a briefing on Tuesday.

"We must endeavor to take pandemic threats off the table if we can," he said.

Hatchett said that delivering COVID-19 vaccines within 11 months was unprecedented, but not good enough. Had they been developed within 100 days, CEPI's pandemic goal, a COVID-19 vaccine could have been available as early as April 2020.

Dr. Jeremy Farrar, director of Wellcome, said an important lesson from the pandemic has been the need to have systems in place that allow for a rapid response when a crisis arrives.

"None of us believe Omicron will be the last variant or that COVID-19 will be the last pandemic," he said.

Bill Gates, co-chair of the Gates Foundation, said research and development investment should be commensurate with the future risk of pandemics.

The latest Gates pledge brings the charity's investment in CEPI to $270 million over the last five years, and its total pandemic investment to $2 billion.

"We want the world not to forget about how bad this pandemic was," he said.

CEPI made early investments in 14 COVID-19 vaccine candidates, including those from Oxford-AstraZeneca and Novavax, which recently received a World Health Organization emergency listing.

The group is also working on next-generation COVID-19 vaccines effective across variants and future coronaviruses in the same family. (Reporting by Julie Steenhuysen; Editing by Bill Berkrot)