Live measles vaccine prevents infection and is recommended as measles, mumps, and rubella (MMR) for children at 12 to 15 months and 4 to 6 years of age. The MMRV (MMR combined with varicella vaccine) is an alternative vaccine for children 12 months to 12 years of age, provided there are no contraindications, but is associated with a higher rate of febrile seizures following administration. The second dose of MMR is not a booster dose but significantly reduces the primary vaccine failure rate, from <5% to <1%. Contraindications to measles vaccine include immunocompromised states or an immunosuppressive course of corticosteroids (>2 mg/kg/day for >14 days); pregnancy; or recent administration of immunoglobulin (3 to 11 months, depending on dose). MMR vaccination is recommended for all HIV-infected persons without evidence of severe immunosuppression (low age-specific total CD4 T-lymphocyte count or a low CD4 T-lymphocyte count as a percentage of total lymphocytes), children with cancer in remission who have not received chemotherapy in the previous 3 months, and children who have not received immunosuppressive corticosteroids in the previous month. Susceptible household contacts with a chronic disease or who are immunocompromised should receive postexposure prophylaxiswith measles vaccine within 72 hours of measles exposure or immunoglobulin within 6 days of exposure.
Rubella, also known as German measles or 3-day measles,is caused by a single-stranded RNA virus with a glycolipid envelope and is a member of the togavirus family. Humans are the only natural host. Rubella virus invades the respiratory epithelium and disseminates via a primary viremia. Afterreplication in the reticuloendothelial system, a secondaryviremia ensues, and the virus can be isolated from peripheral blood monocytes, cerebrospinal fluid, and urine. Rubellavirus is most contagious through direct or droplet contactwith nasopharyngeal secretions from 2 days before until5 to 7 days after rash onset, although virus may be present innasopharyngeal secretions from 7 days before until 14 days after the rash.
Infection in utero results in significant morbidity from congenital rubella syndrome (CRS) with associated ophthalmologic, cardiac, and neurologic manifestations (see Chapter 66).Maternal infection during the first trimester results in fetalinfection with generalized vasculitis in more than 90% of cases.Infants with congenital rubella may shed the virus in nasopharyngeal secretions and urine for longer than 12 months afterbirth and may transmit the virus to susceptible contacts.
In unvaccinated populations, rubella usually occurs in the spring, with epidemics occurring in cycles of every 6 to 9 years. Approximately 25% to 50% of cases are subclinical. Fewer than 20 cases of rubella now occur annually in the United States. Outbreaks of rubella occasionally occur in nonvaccinated groups from internationally imported cases. Transplacental antibody is protective during the first 6 months of life.
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