Countries that are advanced in their vaccination programmes are seeing cases of COVID-19 decline, hospitalizations decrease and early signs of some kind of normality resume.

However, the global picture is far more concerning.

At no point in this pandemic have we seen such an acute need to look to the future challenges and not rest on the patchy achievements made so far.

We are seeing the traumatic effects of the terrible surge of COVID-19 in South Asia – a surge which has also severely impacted global vaccine supplies.

We are also witnessing why access to vaccines before a surge occurs is so important. For that reason, we must focus on ensuring countries who have not benefitted from these life-saving tools do so now, and with urgency.

As the global mechanism for equitable access to COVID-19 vaccines, COVAX has proven it works. Designed and implemented in the midst of an unprecedented global public health crisis, it has delivered over 70 million doses to 126 countries and economies around the world since February – from remote islands to conflict settings – managing the largest and most complex rollout of vaccines in history. Over 35 countries received their first COVID-19 vaccine doses thanks to COVAX.

However, the terrible surge of the virus in India has had a severe impact on COVAX's supply in the second quarter of this year, to the point where, by the end of June we will face a shortfall of 190 million doses.

Even though COVAX will have larger volumes available later in the year through the deals it has already secured with several manufacturers, if we do not address the current, urgent shortfall the consequences could be catastrophic.

But we can meet this challenge with concerted action and global leadership.

Millions of dollars and doses were committed to COVAX on 21 May, bringing the total of doses pledged so far to more than 150 million. At the World Health Assembly, governments have been united in recognizing the political and financial urgency of supporting COVAX with doses and dollars. It is now imperative to build on this momentum to secure full funding for COVAX and more vaccines – right now – for lower income countries at the Advance Market Commitment Summit on 2 June.

If the world's leaders rally together, the original COVAX objectives – delivery of 2 billion doses of vaccines worldwide in 2021, and 1.8 billion doses to 92 lower income economies by early 2022 are still well within reach.

But it will require governments and the private sector to urgently unlock new sources of doses, with deliveries starting in June, and funding so we can deliver. COVAX has the infrastructure in place to facilitate and coordinate this complex global effort.

To enable COVAX to deliver on the promise of global equitable access, we call for the following immediate actions:

• Fund the Gavi COVAX Advance Market Commitment (AMC). The AMC mechanism is how COVAX provides doses to lower income economies. Thanks to the generosity of its donors, the AMC has already secured 1.3 billion doses for delivery in 2021. This is enough to protect the most at-risk population groups: health workers, the elderly and those with underlying health conditions. We need an additional $2 billion to lift coverage in AMC countries up to nearly 30%, and we need it by June 2 to lock in supplies now so that doses can be delivered through 2021, and into early 2022.

• Share doses, now. The pandemic has just taken a frightening new turn, as a deadly surge of cases rages across South Asia and other hotspots. Countries with the largest supplies should redirect doses to COVAX now, to have maximum impact.

  We are starting to see countries stepping forward with doses, with the United States and Europe collectively pledging to share 180 million doses. But we still need more, we need them to go through COVAX, and we need them to start moving in early June. At least one billion doses could be shared by wealthy countries in 2021.

  COVAX's need for doses is greatest right now. Countries with higher coverage rates, which are due to receive doses soon should swap their places in supply queues with COVAX so that doses can be equitably distributed as quickly as possible.

• Free up supply chains by removing trade barriers, export control measures, and other transit issues that block, restrict or slowdown the supply and distribution of COVID-19 vaccines, raw materials, components and supplies.

Now more than ever, at the peak of the pandemic, we need ambitious, global solutions. When it comes to worldwide vaccine distribution, COVAX is the only initiative capable of rising to the challenge of this moment.

It's understandable that some countries want to press ahead and vaccinate all of their populations. By donating vaccines to COVAX alongside domestic vaccination programmes, the most at-risk populations can be protected globally, which is instrumental to ending the acute phase of the pandemic, curbing the rise and threat of variants, and accelerating a return to normality.

COVAX is hugely appreciative to France, Germany, Italy, New Zealand, Spain, Sweden and the UAE for their initial commitments to donate doses through COVAX, and to Canada for funding to support the design and operationalization of the COVAX dose sharing mechanism. We also welcome announcements by the USA, Norway, Croatia, Romania, Australia and Portugal to donate doses to countries in need and we put COVAX forward as the proven mechanism for global, rapid and equitable distribution to facilitate this.

Since COVAX was established in mid-2020, it has had the support and resources of 192 of the world's economies. This tremendous vote of confidence has enabled us to demonstrate our ability to deliver an unprecedented global rollout. It's time to finish the job.