Population diversity in batches of the varicella Oka vaccine.

The Oka vaccine is a live attenuated vaccine for the prevention of varicella. Although the vaccine differs from the progenitor virus by over 40 mutations, only three of these are fixed, the rest being a mixture of the wildtype and the vaccine allele. To examine the extent of this variability between two of the three commercially available vaccine preparations, we analysed the vaccine/wildtype allele frequencies present at fifteen vaccine loci in five preparations each from two different manufacturers of the vOka vaccine. Our results suggest that differences in manufacturing processes between the two companies have resulted in significant variation in the frequencies of the vaccine/wildtype alleles in their vaccines. Yet despite these differences, the allele frequencies in the vaccines from the two companies are strongly correlated. We discuss the significance of these findings and the role of evolutionary processes that influence the production of this live attenuated vaccine.