The new policy was laid out in a memo to advertising clients seen on Thursday by Reuters, which said the company from this week was allowing ads from government entities, hospitals, medical providers and non-governmental organisations that want to get relevant information out to the public. It said the plan for ads from political organisations would be announced in coming days.
"Currently we do not allow such ads to run under our Sensitive Events policy, which is designed to protect users by blocking ads that try to capitalise on short-term events like natural disasters," said the memo, which was sent from Google's head of industry for elections, Mark Beatty, and first reported by Axios.
"However, coronavirus has become an ongoing and important part of everyday conversation, including a relevant topic in political discourse and for many advertisers in different sectors," it said.
Several Democratic strategists told Reuters they welcomed the policy shift.
"We don't have an understanding of the timeframe yet and that's something we're very eager to understand, to make sure we're not continuing to bolster Trump's megaphone," said Mark Jablonowski, the chief technology officer and managing partner of progressive digital ad firm DSPolitical.
He had previously criticised Google's ban, saying it could boost President Donald Trump and Republicans at the November elections.
"It's obviously the right move to reverse this ban. I don't know how Google ever thought that this was a tenable position," said Patrick Stevenson, the Democratic National Committee's chief mobilisation officer.
"This is only one of many policy choices Google has made that has benefited Trump's re-election campaign, and we hope this is a sign that Google intends to look more critically at the role they are playing in this election," he added.
The Trump campaign did not immediately respond to a request for comment.
Google told Reuters the lifting of restrictions for some advertisers will be applied across its platforms.
A company spokeswoman also said Google would evaluate whether to allow brands and private companies to run coronavirus-related ads.