Finally, some good news: The outlook for the global economy is clearly improving.

The Organization for Economic Cooperation and Development unveiled major upgrades to its global forecast on Tuesday. It said that “economic prospects have improved markedly in recent months,” pointing to the deployment of coronavirus vaccines and additional stimulus announcements.

The Paris-based agency now expects the world economy to grow by 5.6% in 2021, an improvement of more than one percentage point from its estimate in December.

The US economy is predicted to expand by 6.5% this year, over three percentage points better than the December forecast. The agency pointed to the effects of “strong fiscal support” from President Joe Biden’s $1.9 trillion stimulus package.

But the OECD also emphasized that extreme uncertainty remains, and that plenty of factors could jeopardize the recovery.

One example: Investors have become increasingly concerned that a rush of activity could trigger a spike in prices later this year, forcing central banks to raise interest rates or taper bond purchases sooner than expected.

According to the OECD, a rebound in demand, especially from China, is pushing up food and metals prices, while oil prices have staged a strong comeback. But the group said it will be essential for policymakers to keep the stimulus coming, even if inflation overshoots some targets.

Other threats

The possibility of a sharp rise in prices is far from the only fear.

The agency noted that vaccine campaigns are moving at different speeds around the world, and coronavirus variants that resist vaccines could still emerge.

“Slow progress in vaccine rollout and the emergence of new virus mutations resistant to existing vaccines would result in a weaker recovery, larger job losses and more business failures,” it said in its report.

The OECD also said that it’s essential that governments maintain their support for the economy even as the situation starts to brighten. European Central Bank President Christine Lagarde has issued a similar warning, cautioning that countries should not “brutally” pull stimulus.

“A premature tightening of fiscal policy must be avoided,” the group said.

Another worry is high levels of debt. The OECD focused on corporate debt loads, in particular, with debt servicing burdens at or above their level during the 2008 financial crisis even though interest rates are at historic lows.

“Although some firms have used borrowing to build up sizable cash buffers since the onset of the pandemic, high leverage could moderate new investment,” it said. If the recovery is slower than expected, or government support programs end too soon, this could “trigger additional debt delinquencies or defaults.”

Right now, these are just hypotheticals. But so are expectations of booming growth, which are due to play out in the coming months. The OECD report is a reminder that while the outlook is brightening, it’s also tentative.