TRENTON, N.J. (AP) -- Young children needing immunization against chickenpox and three other diseases likely will have to get an extra shot, due to manufacturing problems that have halted production of a four-disease combo vaccine made by Merck & Co.Merck said Thursday that its ProQuad vaccine, which protects against measles, mumps and rubella as well as chickenpox, won’t be available from about July until at least year’s end.>>> Discuss This Story
