AstraZeneca must provide reassurance that it will not profit from its potential Covid-19 vaccine, non-governmental organisation Medecins Sans Frontieres (MSF) said on Tuesday, urging the company to make public its supply contracts.

The British firm said on Monday its Covid-19 vaccine was 70% effective in pivotal trials and could be up to 90% effective, giving the world's fight against the global pandemic a third new weapon that can be cheaper to make, easier to distribute and faster to scale-up than rivals.

AstraZeneca has said it will not profit from sales of its vaccine while Covid-19 is considered a pandemic. The price of its candidate has been set at about $3 per dose, against at least four times more for other candidates.

"MSF welcomes AstraZeneca's commitment to sell the vaccine at a 'no-profit' price during the pandemic, but the reality is that it's an empty promise unless we're able to substantiate these important claims with data," said Roz Scourse of medical group MSF, also known as Doctors Without Borders.

The organisation urged AstraZeneca to disclose the contracts signed with governments for its vaccine and said there could be clauses that limit the price until the company declares the end of the health emergency, which could be as early as July.

AstraZeneca said it would look for international consensus on when the pandemic phase of Covid-19 was over, rather than a particular date.

"From the outset, AstraZeneca's approach has been to treat the development of the vaccine as a response to a global public health emergency, not a commercial opportunity," an AstraZeneca spokesman said.

"We continue to operate in that public spirit and we will seek expert guidance, including from global organisations as to when we can say the pandemic is behind us."

The GAVI vaccine alliance said Monday's efficacy data was "positive news for the COVAX vision of equitable access" for vulnerable groups.

It said the hundreds of millions of doses had been secured on behalf of COVAX, a procurement scheme co-led by the World Health Organization designed to secure rapid and fair global access to Covid-19 vaccines.