* Pfizer update on coronavirus vaccine sends shares, oil higher

* Soybeans already supported by strong demand, S. America dryness

* Grain market awaits USDA supply/demand update on Tuesday (New throughout, adds analyst comments and latest prices, changes byline/dateline, previous PARIS/SINGAPORE)

CHICAGO, Nov 9 (Reuters) - U.S. soybean futures reached a new four-year high on Monday as the first successful data from a late-stage COVID-19 vaccine trial fueled hopes of the economy recovering quickly from the pandemic-driven crisis.

Broad-based optimism about Pfizer's vaccine trials added support to a soybean market already buoyed by strong Chinese demand and weather risks in South America.

The "positive ramifications of Pfizer news today cannot be overstated," said Rich Feltes, a grain analyst and head of market insights for U.S. futures brokerage RJ O'Brien.

Traders were adjusting positions in the market before the U.S. Department of Agriculture issues a monthly report on Tuesday that is expected to trim the government's estimates for U.S. soybean yields and inventories.

An uptick in demand from China, the world's top soybean importer, this summer and fall has helped to draw down U.S. soy ending stocks.

The USDA, in a daily reporting system for export sales, said on Monday that exporters sold 123,000 tonnes of U.S. soybeans to unknown destinations.

The deals are "a continuation of post-election buying," Feltes said, after USDA on Friday announced separate U.S. soybean export sales to China and unknown buyers.

The most-active soybean contract on the Chicago Board of Trade (CBOT) was up 11-1/4 cents at $11.12-3/4 a bushel by 11:45 a.m. CST (1745 GMT). It earlier rose to $11.18, its highest since July 2016 and surpassing a previous four-year high of $11.12-3/4 struck last week.

Most-active corn futures were up 1-1/2 cents at $4.08-1/4 a bushel, while wheat was down 1-1/2 cents at $6.00-1/2 at the CBOT.

The USDA, in its supply and demand report on Tuesday, is expected to reduce its estimate for U.S. corn ending stocks, according to a Reuters survey of analysts.

(Reporting by Tom Polansek in Chicago, Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Marguerita Choy)