Unintentional Administration of Varicella Virus Vaccine --
United States, 1996
Since June 1995, seven separate cases of unintentional
administration of varicella virus vaccine (Varivax{Registered} *)
to
pregnant women have been reported in the United States to the
Varivax{Registered} Pregnancy Registry **. All seven women had
household exposure to varicella, and varicella zoster immune
globulin (VZIG) prophylaxis was indicated. However,
Varivax{Registered} was administered unintentionally instead of
VZIG to these women. One of the women received five times the
recommended dose of vaccine. All had negative histories for
varicella, and the status of their immunity to varicella before
receiving the vaccine was not reported to the registry. Gestational
age at vaccination ranged from 6 to 31 weeks; four of the seven
pregnancies were less than 20 weeks' gestation. Two of these women
have since delivered healthy infants; pregnancy outcomes are
pending for five women.
Reported by: JM Manson, PhD, RG Sharrar, MD, Merck Research
Laboratories, Worldwide Product Safety and Epidemiology Div, West
Point, Pennsylvania. Vaccine Safety and Development Activity, Child
Vaccine Preventable Diseases Br, Epidemiology and Surveillance Div,
National Immunization Program, CDC.
Editorial Note
Editorial Note: The use of Varivax{Registered} is contraindicated
during pregnancy (1) because its effects on the fetus are unknown
and because infection with wild varicella zoster virus during the
first half of pregnancy may result in congenital varicella syndrome
(2). The Advisory Committee on Immunization Practices recommends
that VZIG be used for postexposure prophylaxis in susceptible
persons at high risk for varicella complications, including women
exposed to varicella at any stage of pregnancy (1). The risk for
congenital varicella syndrome after natural infection with wild
varicella zoster virus is 1%-2%; because the virulence of the
attenuated virus used in the vaccine is less than that of the
wild-type virus, the risk to the fetus, if any, should be lower
(1).
Two potential reasons these incidents occurred are 1) use of
the wrong vial by mistake and 2) a lack of understanding of the
appropriate indications for the use of these two products. These
cases underscore the need for health-care providers and pharmacists
to carefully check product labels before administering any drug and
to read the package inserts for any drug if they are uncertain of
the appropriate indications for its use. VZIG is shipped as a
liquid in 2-mL or 10-mL vials and must be stored at 36 F-46 F (2
C-8 C). In
contrast, Varivax{Registered} is shipped as a lyophilized
powder for suspension in 0.7-mL vials, must be reconstituted with
diluent before use, and must be stored at 5 F (-15 C).
Before a vaccine or any drug is administered to a woman of
childbearing age, a health-care provider should be careful to
obtain a history of pregnancy or intended pregnancy from the
patient. Health-care providers are strongly encouraged to enroll
any women who were unintentionally vaccinated with varicella virus
vaccine 3 months before or at any time during pregnancy in the
Varivax{Registered} Pregnancy Registry, telephone (800) 986-8999.
References
CDC. Prevention of varicella: recommendations of the Advisory
Committee
on Immunization Practices (ACIP). MMWR 1996;45(no. RR-11).
Enders G, Miller E, Cradock-Watson J, Bolley I, Ridehalgh M.
Consequences of varicella and herpes zoster in pregnancy:
prospective
study of 1739 cases. Lancet 1994;343:1548-51.
Use of trade names and commercial sources is for identification
only and does not imply endorsement by the Public Health Service or
the U.S. Department of Health and Human Services.
** This registry is maintained jointly by Merck and Company and by
CDC; Merck and Company is responsible for daily management and
operation of the registry. The registry was established to
determine the risk for congenital varicella syndrome or other birth
defects following vaccination with Varivax{Registered} 3 months
before or at any time during pregnancy.
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