Brent crude futures were up 40 cents at $55.44 a barrel by 05:11 GMT, while U.S. West Texas Intermediate (WTI) gained 28 cents to $52.48. Both benchmarks gained nearly 8% in January.
Oil prices have been boosted by vaccination programmes getting underway in hard-hit countries and output cuts by major producers like Saudi Arabia. But euphoria over a possible end to the pandemic has been undermined by the slow pace of vaccinations and the rise of new variants of the coronavirus.
Still, with more vaccines proving successful in trials and infections falling in some areas, demand for oil and fuels is likely to pick up as more of the world's population gets inoculated against COVID-19.
U.S. oil and gas drillers are gearing up for a pickup in demand and as higher prices make news wells profitable again, adding rigs for a sixth month in a row in January.