TOKYO, Nov 30 (Reuters) - Japanese government bonds (JGBs) gained on Tuesday, in line with U.S. Treasuries, after the chief of U.S. drugmaker Moderna said COVID-19 vaccines are unlikely to be as effective against the Omicron variant as it has been with other types.

Benchmark 10-year JGB futures gained 0.20 point to 151.94, with a trading volume of 29,266 lots.

The yield on the benchmark 10-year cash JGBs fell 1.5 basis point to a three-week low of 0.055%.

The 20-year yield fell 2.0 basis points to 0.450% while the 30-year bond yield also shed 2.0 basis points to 0.665%.

Moderna Chief Executive Officer Stéphane Bancel told the Financial Times that COVID-19 vaccines are unlikely to be as effective against the Omicron variant as they have been previously.

The news sparked a fresh wave of selling in risk assets, with Japan's Topix stock index hitting a three-month low, and buying in low-risk assets such as bonds. (Reporting by Tokyo Markets Team; Editing by Sherry Jacob-Phillips)