NEW DELHI (BLOOMBERG) - For months, developed economies have hoarded Covid-19 vaccines and the raw materials needed to make them. Now, they're being forced to act as an explosive outbreak in India raises the risk of new virus mutations that could threaten the wider world.

Under mounting criticism for dominating vaccine resources, the United States said this week that it will help India by sending items needed to manufacture vaccines as part of an aid package. European countries are also pledging help as new cases in the South Asian country smash world records.

US President Joe Biden's administration is separately vowing to share its stockpile of AstraZeneca vaccines - which the US hasn't even approved for use - and meeting with drug companies about boosting supply and waiving intellectual property protections on Covid-19 shots, a shift India and South Africa have been pushing for.

The moves show a growing realisation that the vaccine nationalism many wealthy nations have embraced has the potential to backfire, prolonging the global pandemic.

While those countries have been cornering supplies of the first vaccines for their world-leading roll-outs, places like India have run short, allowing the virus to run wild. Some scientists have linked the nation of 1.3 billion people's second wave to a more virulent strain, with the out-of-control outbreak providing a petri dish for further mutations to evolve that could challenge the vaccines now being distributed from Britain to Israel.

"There is certainly potential for new variants to emerge in a country the size of India that could pose a threat elsewhere," said Mr Ramanan Laxminarayan, founder of the New Delhi and Washington-based Centre for Disease Dynamics, Economics and Policy. "It is in the world's interest to ensure that India exits the pandemic at the earliest, and vaccination is the only way."

While viruses undergo changes all the time, not all are significant. But some new strains in other parts of the world have ignited concerns because they could be more contagious. Earlier this year, data showed that AstraZeneca's vaccine was less effective against one variant that emerged in South Africa.

India's variant - a strain named B1617 - is already raising alarms. It has two critical mutations that make it more likely to transmit and escape prior immunity that has been built up, Dr Anurag Agrawal, the director of India's Council of Scientific and Industrial Research's genomics institute, said last week.

Dr Rakesh Mishra, the director of the Centre for Cellular and Molecular Biology in Hyderabad, one of the labs working to sequence virus samples in India, said this variant appears to be more infectious, but it isn't likely to cause more deaths.

Also, the AstraZeneca vaccine and another from India's Bharat Biotech International have been shown to be effective against it in preliminary data, he said. India's health ministry hasn't confirmed if this variant is more transmissible, and a spokesman for the federal health ministry could not be immediately reached.

And at the rate infections are occurring in India, B1617 won't be the only or last variant of concern out of India's second wave.

"I fear there may be more trouble coming," said Dr William Haseltine, a former Harvard Medical School professor and HIV researcher who now chairs think-tank Access Health International. "There are already second- and possibly third-generation variants of the B1617 circulating in India. These may be more dangerous than is the B1617 variant itself."

India's second wave is certainly more destructive. Hospitals and crematoriums are cracking under pressure, while Indians are begging on social media for everything from oxygen cylinders to drugs. Almost 3,000 people are dying every day, with experts saying that figure likely underplays the real toll. The daily death rate is almost double what it was at the height of the first wave, stoking speculation the new variant, or other mutations, are to blame.

Brazil, another developing country that has struggled to ramp up vaccines, suffered from a virus strain that's said to be responsible for a much higher Covid death rate.

Public health experts now see a ramped-up vaccination effort as key to quelling outbreaks like the one in India.

But despite being home to the world's largest vaccine industry, India's immunisation drive has slowed in recent weeks and many states are warning that their supplies have almost dried up.

The shortages have partly been blamed on bottlenecks related to a few key items, with Mr Adar Poonawalla - the chief executive officer of the Serum Institute of India, the country's biggest vaccine producer and AstraZeneca's manufacturing partner - increasingly pointing to the US.

Mr Poonawalla has repeatedly called on the US to release shipments of critical raw materials, saying the US invoking the Defence Production Act to curb exports of some ingredients and bolster its own industry is one of the main reasons behind the slowdown in shots.

"It's the shortage of critical input materials that is becoming a real bottleneck," Rajinder Suri, chief executive officer of the Developing Countries Vaccine Manufacturers' Network, said at a briefing last Friday (April 23). "If anyone of the components is missing, the entire chain comes to a grinding halt. The problem is that most of these materials are coming from the US."

The items that many vaccine makers have been struggling to get hold of include glass vials, single-use filters and bioreactor bags, according to the majority of 15 suppliers, developers and contract manufacturers surveyed ahead of a Chatham House summit last month. However, the scale of the problem, even within industry groups, has been hard to quantify due to a lack of data.

As the scale of India's virus emergency rose to global prominence this week, the offers of aid and doses started to come. Besides the US' commitments, Britain, France and Germany have also pledged aid and much needed oxygen tanks for India.

Still, a more marked shift in the way developed countries view vaccines will likely be needed. Even if the US did send all of its 60 million AstraZeneca doses to India, it would have a limited impact on a population of its size. There are also other parts of the vast developing world that are yet to see shots, or consistent supplies.

"Many parts of the world still remain deeply at risk," Dr Jennifer Nuzzo, a senior scholar at The Johns Hopkins Centre for Health Security, said last week. "I worry about these headlines continuing for a year or more unless international partners get together and help share some of the vaccines that are there."