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Notice to Readers: Supply of Vaccines Containing Varicella-Zoster Virus
CDC received notice from Merck & Co., Inc., that it has lower amounts of varicella-zoster virus (VZV) than expected
from recently manufactured bulk vaccine. Bulk vaccine
production is an intermediate step in the manufacture of
VZV-containing vaccines. Varicella bulk is stored frozen until it is needed in the final preparation phase of each
vaccine. Production of VZV bulk has been suspended temporarily while the manufacturer identifies the cause of the low virus yield. Merck is the only
U.S. supplier of VZV-containing vaccine, including varicella vaccine
(Varivax®); combined measles, mumps, rubella, and
varicella (MMR-V) vaccine
(ProQuad®); and zoster vaccine
(Zostavax®). This lower virus yield does not affect the quality of any
of Merck's VZV-containing vaccines currently on the market, any lots of vaccine manufactured and ready for release to
the market, or any VZV-containing vaccines presently being manufactured.
To conserve existing bulk vaccine with adequate VZV
potency, Merck is prioritizing continued production of varicella
and zoster vaccines over production of MMR-V vaccine. Merck is taking this approach because the production of varicella
vaccine requires less VZV than the production of MMR-V
vaccine. Although zoster vaccine requires a similar amount of VZV
for production as MMR-V vaccine, projected supply needs for zoster vaccine are much lower than projected supply needs
for MMR-V vaccine. Merck also will increase production of combined measles, mumps, and rubella (MMR) vaccine
(M-M-R II®).
Current supply assessments in the United States indicate that this interruption in bulk vaccine supply will not affect
the supply of either varicella vaccine or zoster vaccine. The U.S. varicella vaccine supply is expected to be adequate to
fully implement the recommended immunization schedule for
varicella vaccine for all age groups, including the
routine 2-dose schedule for children at 12--15 months and at 4--6 years, catch-up vaccination with the second dose for children
and adolescents who received only 1 dose, and vaccination with 2 doses for other children, adolescents, and adults
without evidence of immunity (1--3). For zoster vaccine, the supply is expected to be adequate to vaccinate adults aged
>60 years in accordance with current provisional vaccine policy recommendations
(4). The MMR-V vaccine supply is adequate to
continue ordering this combination vaccine
(5); however, the manufacturer expects supplies of MMR-V vaccine to be depleted
toward the end of 2007, depending on market demand. When this occurs, supplies of separate MMR and varicella vaccines
are expected to be adequate to fulfill the need for these two products in place of MMR-V vaccine. CDC will continue to
work with Merck and vaccine-provider stakeholders to monitor the supply of VZV-containing vaccines. Updates on
vaccine shortages and delays are available at
http://www.cdc.gov/nip/news/shortages/default.htm.
Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of
Health and Human Services.References to non-CDC sites on the Internet are
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endorsement of these organizations or their programs by CDC or the U.S.
Department of Health and Human Services. CDC is not responsible for the content
of pages found at these sites. URL addresses listed in MMWR were current as of
the date of publication.
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