Characterization of measles viruses isolated after measles vaccination.

Seven measles virus (MV) strains were isolated from children who developed clinical signs of fever and rash 3-9 days after measles vaccination. The nucleotide sequence of the H gene, the molecular size of the H protein, the haemadsorption activity on African green monkey red blood cells, and antigenicity as determined by virus neutralization revealed that one strain was of the vaccine type and the remaining six were the wild virus type. Isolation of the virus directly from patients suspected of a vaccine-induced side-reaction and subsequent characterization of such isolated virus may be useful in differentiation between vaccine-induced side-reactions and natural measles.