Reduction in titer of Rotarix by breast milk from India and United States. Selected breast milk specimens with low and high neutralizing titer from the United States (A, B) and India (C, D) were tested for reduction in viral titer as described in the text. While breast milk with low titers demonstrated only modest neutralization activity that was quenched with dilution, breast milk with higher titer, particularly those from India, could be diluted 1:128–1:512 and still neutralize the vaccine virus. NT indicates neutralizing titer.