At the opening of European markets, the dollar climbed by 1%, the offshore-traded yaun while Australian dollar and Norwegian crown fell.
The fall of the dollar index has advanced other currencies. The Chinese yuan struck a 28-month peak, the New Zealand dollar rose 0.6% to hit a 19-month high and the Australian dollar made a seven-week top.
The greenback index has stood at 92.641 against a basket of six major currencies, close to a two-week low.
Pfizer Inc and BioNTech announced on Monday that the result of their clinical trial for COVID-19 vaccine has proven to be more than 90% effective.
The dollar, which has held above a two-year low hit on Thursday of 92.495, was down nearly 0.1% against a basket of currencies at 93.643, after shedding gains made in Asian trading.
Stocks sold off on Monday and the currency market saw "risk-off" moves, with the dollar index climbing to its highest in six-weeks.
The euro fell to a two-month low on Wednesday, the dollar edged up to $1.1671 per euro, its highest since July 27.
The dollar index fell 0.3% at 92.836. Markets are keen to see the Fed's economic projections, and particularly whether it spells out where it sees inflation headed and what exactly that means for interest rates.
The pound's recent recovery against a weaker dollar was interrupted on Thursday when the dollar strengthened following the US Federal Reserve meeting, while investors' attention turned to the Bank of England's policy meeting.
The dollar gave up gains made after the Federal Reserve upgraded its 2020 economic forecast this week to trade in negative territory on Thursday. It was last quoted at 92.923 against a basket of major currencies, on track for a 0.3% weekly loss.