SHANGHAI, Nov 30 (Reuters) - China's blue-chips closed lower on Tuesday after U.S. drugmaker Moderna set off fresh alarm bells about the Omicron variant, while data showed China's services sector grew at a slightly slower pace amid regional outbreaks of COVID-19 cases.

The blue-chip CSI300 index closed 0.4% lower at 4,832.03, while the Shanghai Composite Index was flat at 3,563.89 points.

** For the month, the CSI300 index went down 1.6%, while the Shanghai Composite Index edged up 0.5%.

** Chinese shares weakened slightly in afternoon trade after the head of drugmaker Moderna told the Financial Times that COVID-19 vaccines are unlikely to be as effective against the Omicron variant of the coronavirus as they have been against the Delta variant.

** Activity in China's services sector grew at a slightly slower pace in November, as the sector took a hit from fresh lockdown measures as authorities raced to contain the latest outbreak.

** Analysts say the services sector is more vulnerable to sporadic COVID-19 outbreaks, clouding the outlook for the much-anticipated rebound in consumption in the months ahead.

** Consumer staples dropped 2.3% and tourism shares shed 0.5%.

** Meanwhile, China's factory activity grew for the first time in three months as the crippling surge in raw material prices and power rationing eased.

** "There are also weak links as seen in the subcomponents, such as the underperformance of small businesses and shrinking employment indices in both manufacturing and services sectors," HSBC analysts said in a note.

** "This implicates that policymakers still need to lend more targeted support to these sectors."

** Information technology firms, semiconductors and defence stocks gained between 1% and 2.4%. (Reporting by Shanghai Newsroom; Editing by Sherry Jacob-Phillips)