GENEVA (Reuters) - The World Health Organization hopes to have half a billion doses of COVID-19 vaccines available for distribution by the global COVAX initiative in the first quarter of 2021, its chief scientist said on Friday.

To date 189 countries have joined the COVAX programme, which is backed by the WHO and seeks to ensure equitable distribution of vaccines. The United States is not among them, having secured bilateral deals.

The initial COVAX plan is to vaccinate the 20% of populations at highest risk, including health workers and people aged over 65.

“The goal is to get at least 2 billion doses by end of 2021 which will be enough to vaccinate 20% of the populations of countries that are part of COVAX,” chief scientist Soumya Swaminathan told a Geneva news conference.

This would be enough to “bring to an end the acute phase of the pandemic” by reducing mortality and the impact on health systems, she said.

“Our goal, our hope is that in the first quarter of 2021 that we would have about half a billion of doses available to be distributed across the countries, in a fair manner,” Swaminathan said.

“So countries can start expecting doses toward the end of the first quarter of 2021. A few countries may start earlier, it’s likely, possible, that we may have some learnings by going early into a few countries,” she said without elaborating.

“But then the majority, the bulk of the tranches would probably start moving out in the second quarter of 2021.”

COVAX is co-led by the GAVI vaccines alliance, the WHO and the Coalition for Epidemic Preparedness Innovations (CEPI).