Longer-term US Treasury yields were lower on Tuesday as investors tried to judge how quickly vaccines could be distributed to fight the COVID-19 pandemic.

The benchmark 10-year yield was down 1.3 basis points in afternoon trading at 0.9146%.

It traded as low as 0.893% in the morning, its first time below the 0.9% threshold since Dec. 1, before rising in step with higher equity markets.

Investors seemed to be trying to judge how widely and quickly vaccines would be available, which will determine the pace of reopening plans and economic recovery, said Eric Jussaume, director of fixed income for Cambridge Trust. With a lack of clarity on the schedule, "Enthusiasm could be postponed a little bit," he said.

Britain on Tuesday became the first Western nation to begin a mass inoculation campaign. In the United States, the Trump administration sought to shore up the vaccine supply, after a report that Pfizer Inc may not be able to provide more of its vaccine there until next June because of commitments to other countries.

After opening lower on Tuesday, the S&P 500 and the Dow reversed course while the Nasdaq hit a record high.

An afternoon US Treasury auction of $56 billion of 3-year notes produced average results according to a research note from BMO Capital Markets analyst Ben Jeffery, with a high yield of 0.211% and dealers accounting for 34.9% of accepted bids.

A closely watched part of the US Treasury yield curve measuring the gap between yields on two- and 10-year Treasury notes, seen as an indicator of economic expectations, was at 76 basis points, about 2 basis points lower than on Monday's close.

The two-year US Treasury yield, which typically moves in step with interest rate expectations, was up less than a basis point at 0.1508% in afternoon trading.