Cheap, but useless. :-( No peer reviewed research shows that sodium bicarbonate can build an effective immunity to influenza.
I doubt you’ll accept that argument, so try this one: if sodium bicarbonate was effective, then medical insurance companies would save billions of dollars by refusing to cover unnecessary and expensive flu vaccines. However, I don’t know of any medical insurer which recommends sodium bicarbonate to prevent catching the flu.
p://imva.info/index.php/2009/11/arm-hammer-soda-company