Bloch gain in quantum cascade lasers

PCT No. PCT/GB94/01646 Sec. 371 Date Feb. 8, 1996 Sec. 102(e) Date Feb. 8, 1996 PCT Filed Jun. 29, 1994 PCT Pub. No. WO95/05194 PCT Pub. Date Feb. 23, 1995The invention provides the use of Hepatitis A virus capsid, or a mucosally immunogenic fragment or epitope thereof, for the manufacture of a mucosal vaccine composition for administration to a mucosal surface of a patient to induce production of serum Immunoglobulin G antibody against Hepatitis A. Preferably the vaccine composition is administered by the intranasal route.