* Asian stock markets : tmsnrt.rs/2zpUAr4 * MSCI ex-Japan, off 0.4%, Nikkei tries to bounce * S&P 500 futures -0.7% on doubts over vaccine rollouts * Retail crowd turns gaze on silver, jumps to 6-mth high * Dollar supported by cautious mood, bonds brace for supply SYDNEY, Feb 1 (Reuters) - Asian shares wavered on Monday amid worries that problems with vaccine rollouts combined with new strains of COVID-19 will delay a global economic recovery that has already been baked into the market’s rich valuations. MSCI’s broadest index of Asia-Pacific shares outside Japan fell 0.4%, following four straight sessions of losses. Japan’s Nikkei bounced 0.4%, after shedding almost 2% on Friday. Futures for the S&P 500 lost another 0.7% in heavy trade, while NASDAQ futures fell 0.9%. Dealers were also warily awaiting new developments in the headline-grabbing battle between retail investors and funds that specialise in shorting stocks. U.S. hedge funds bought and sold the most stock in more than 10 years amid wild swings in GameStop Corp, according to an analysis by Goldman Sachs Inc. Talk on Monday was that silver was the new target for the retail crowd as the metal jumped 5.7% to a six-month high . Yet many analysts see this entertaining episode as a sideshow compared to signs of a loss of momentum in the United States and Europe as coronavirus lockdowns bite. Indeed, a survey from China on Sunday showed factory activity grew at the slowest pace in five months in January as restrictions took a toll in some regions. Neither was the news on vaccine rollouts positive, especially given doubts about whether they will work on new COVID strains. “It is these considerations, not what is happening to a video gamer retailer day to day, that has weighed on risk assets,” said John Briggs, global head of strategy at NatWest Markets. “So much of the market’s valuations, risk in particular, is premised on the fact we can see a light at the end of the COVID tunnel.” Doubts have also emerged about the future of President Joe Biden’s $1.9 trillion relief package, with 10 Republican senators urging a $600 billion plan. The jitters in stocks caused only a brief ripple in bonds with Treasury yields actually rising late last week, perhaps a refection of the tidal wave of borrowing underway. A record $1.11 trillion of gross Treasury issuance is slated for this quarter, up from $685 billion the same time last year. Early Monday, U.S. 10-year yields held at 1.07% and near the recent 10-month top of 1.187%. Higher yields combined with the more cautious market mood have seen the safe-haven dollar steady above its recent lows. The dollar index stood at 90.628, having bounced from a trough of 89.206 hit early in January. The euro idled at $1.2121, well off its recent peak at $1.2349, while the dollar held firm at 104.74 yen. Gold followed silver higher to $1,853 an ounce, but has repeatedly stalled at resistance around $1,875. Global demand concerns kept oil prices in check. U.S. crude eased 30 cents to $51.90 a barrel, while Brent crude futures dropped 20 cents to $54.84.