With a flu season that ­arrived earlier and more harshly than usual, government health officials have been loudly sounding the call for everyone to be immunized, while more quietly encouraging ­efforts to develop a better vaccine that would protect against many more strains of the virus.

The vaccines in use today are only about 60 percent effective, last for only a single flu season, and take months to produce ­— which left Americans initially unprotected in 2009 when the swine flu pandemic arose without much warning.