Moderna will supply 34 million doses of its Covid-19 vaccine this year and Sweden has donated 1 million AstraZeneca shots to the global COVAX programme, a small boost as it struggles to get stocks to inoculate the world's poorest people.

The advance purchase contract agreed with Moderna is for up to 500 million doses, but the roll out will only start in the fourth quarter, with 34 million doses available this year, the GAVI vaccine alliance said on Monday.

The bulk - 466 million - would only become available next year, it said.

The deal expands the programme's pipeline of vaccines to eight and contains options to potentially access doses of variant-adapted vaccines in the future, it said.

The agreement follows the U.S. drugmaker's shot being approved for emergency use listing by the WHO on Friday, a prerequisite for COVAX eligibility.

GAVI runs the COVAX vaccine sharing facility with the World Health Organization.

The Swedish donation is the second by a European Union member after France last month amid mounting concerns about growing inequity in vaccine distribution after wealthy countries built up stocks of shots for its citizens.

The EU also wants the bloc to regain the initiative in vaccine diplomacy from Russia and China.

Sweden paused the use of the AstraZeneca vaccine in March after reports of rare, but serious, blood clots among people who had received that shot. It later resumed the use of the shot, but only for people aged 65 or above.

The WHO has repeatedly urged wealthier countries to share excess doses to help inoculate health workers in low-income countries and tame the pandemic which has killed more than 3.3 million.

But COVAX has also been hit by supply problems for Covid-19 vaccines, notably the AstraZeneca shot made in India, where authorities have restricted exports because of its fast-growing epidemic.

Moderna said in a statement the doses would be offered at its "lowest tiered price" without disclosing further details.

Sweden's donation aims to help address immediate-term supply delays, ensuring some countries can administer second doses to high-risk groups, Gavi said.

Since late February, GAVI has shipped 49 million Covid-19 doses to 121 countries and economies, mainly the AstraZeneca vaccine.

"Expanding and having a diverse portfolio has always been a core goal for COVAX, and to remain adaptable in the face of this continually evolving pandemic – including the rising threat posed by new variants," said Seth Berkley, Gavi CEO.

Berkley said last month that COVAX aimed to deliver one-third of a billion doses by mid-year.

COVAX hopes to have 2 billion doses available by the end of 2021, half of which will go to 92 lower-income countries. In all, depending on how Gavi exercises its options, it has secured up to 3.6 billion doses, a spokeswoman said.