Britain, where some 9 million people have been given their first dose of a vaccine, said it expected its supply of COVID-19 shots would not be interrupted.
The Japanese yen weakened to a fresh 11-week low of 104.95 yen per dollar.
The Swiss franc broke lower from recent ranges to drop more than half a percent to its lowest against the buck since Dec. 2, at 0.8964 francs per dollar.
Despite the dollar's move higher this week, most analysts are sticking to their calls it will weaken in 2021 as the new US government implements massive fiscal spending while the Federal Reserve maintains its ultra-easy monetary policy.
There's such a tug of war right now between the longer-term momentum_and the shorter-term term phenomenon of maybe a dollar short squeeze.
The dollar index against a basket of currencies is up 0.50% this month after falling more than 6% last year. It was last down 0.22% on the day at 90.46.