President Barack Obama is tapping another $2.7 billion in emergency H1N1 flu funding to buy vaccines, antiviral drugs and to make other preparations for an immunization campaign in the fall.Obama had earlier approved $1.8 billion in emergency spending from a $5.8 billion fund set up by Congress as part of this year’s supplemental spending bill.Obama said in a letter to House Speaker Nancy Pelosi (D-Calif.) that he would let her know if more money will be needed.