The yen scraped back some losses against the U.S. dollar on Tuesday, after the safe currency took a drubbing on news of the development of a coronavirus vaccine which raised optimism of a global economic recovery.

U.S. drugmaker Pfizer Inc and German partner BioNTech SE said a large-scale clinical trial showed their vaccine was more than 90% effective in preventing Covid-19.

The yen edged higher to 105.07 against the dollar, after suffering its biggest loss overnight since March. It fetched 76.42 against the Australian dollar, having lost more than 2% overnight.

“What’s important about the overnight movement is that it overturned the current trend of the U.S. dollar falling, instead of the yen, when the market turns risk-on,” said Masafumi Yamamoto, chief currency strategist at Mizuho Securities.

“The yuan and euro have been rising against the dollar as equities jumped on Joe Biden’s election win … But the overnight movement flipped things back to the way it is when markets usually turn risk-on: U.S. Treasury yields rise and the yen depreciates more than the dollar.”

The vaccine news comes as the global tally of Covid-19 infections reached 50.68 million on Monday, stoking worries of more lockdown measures across the globe.

Some analysts said markets over-reacted to the news because questions about the vaccine remain, such as how effective the vaccine is by ethnicity or age and how long immunity may last.

“Perhaps the market did over-react to the vaccine, given there’s still some way to go prove that it’s safe,” said Westpac currency analyst Imre Speizer.

“What they’ve shown is that it’s reasonably effective, safety is another stage. Once the market looked into the finer print of what these results were, maybe they backed off the trade a bit.”

The Australian dollar steadied at $0.7275 against its U.S. counterpart after touching a seven-week high on Monday.

The euro stood little changed at 1.1819, having fallen more than 0.4% overnight.

The prospects of a Biden presidency has boosted risk sentiment as many believe it could boost international trade relations and maintain an easy monetary policy.

Still, incumbent Donald Trump has made no sign of conceding and his campaign is planning a series of rallies to build support for legal fights challenging the election results.

U.S. Senate Majority Leader Mitch McConnell on Monday said President Donald Trump was completely within his rights to look into “irregularities” from the election.

Trump also said he had “terminated” Defense Secretary Mark Esper, signaling he may use his final months in office after defeat at the polls to settle scores within his administration.

Against a basket of currencies, the dollar held steady at 92.75, slightly above Monday’s 10-week trough of 92.12.