Fed doesnt pump in money, literally. What Fed does is open market operations. It is not literally money printing. They have to buy assets, inorder to create money supply in the system. So they are providing broad based liquidity and they are doing it at zero cost. They have also removed the reserve ratio to be maintained by banks. So all of this not literally money printing, like some doom sayers call.
Regarding using money to develop vaccine, it is the govt's job to provide fiscal stimulus or targeted stimulus to certain sectors. What Fed is doing, is its best to prevent/reduce a liquidity/solvency crisis for companies.