Human immunoglobulin given shortly after exposure can attenuate the clinical course of measles. In immunocompetent persons, administration of immunoglobulin within 72 h of exposure usually prevents measles virus infection and almost always prevents clinical measles. Administered up to 6 days after exposure, immunoglobulin will still prevent or modify the disease. Prophylaxis with immunoglobulin is recommended for susceptible household and nosocomial contacts who are at risk of developing severe measles, particularly children <1 year of age, immunocompromised persons (including HIV-infected persons previously immunized with live attenuated measles vaccine), and pregnant women. Except for premature infants, children <6 months of age usually will be partially or completely protected by passively acquired maternal antibody. If measles is diagnosed in a household member, all unimmunized children in the household should receive immunoglobulin. The recommended dose is 0.25 mL/kg given intramuscularly. Immunocompromised persons should receive 0.5 mL/kg. The maximum total dose is 15 mL. IV immunoglobulin contains antibodies to measles virus; the usual dose of 100–400 mg/kg generally provides adequate prophylaxis for measles exposures occurring as long as 3 weeks or more after IV immunoglobulin administration.
The first live attenuated measles vaccine was developed by passage of the Edmonston strain in chick embryo fibroblasts to produce the Edmonston B virus, which was licensed in 1963 in the United States. Further passage of Edmonston B virus produced the more attenuated Schwarz vaccine that currently serves as the standard in much of the world. The Moraten (“more attenuated Enders”) strain, which was licensed in 1968 and is used in the United States, is genetically closely related to the Schwarz strain.
Lyophilized measles vaccines are relatively stable, but reconstituted vaccine rapidly loses potency. Live attenuated measles vaccines are inactivated by light and heat and lose about half their potency at 20°C and almost all their potency at 37°C within 1 h after reconstitution. Therefore, a cold chain must be maintained before and after reconstitution. Antibodies first appear 12–15 days after vaccination, and titers peak at 1–3 months. Measles vaccines are often combined with other live attenuated virus vaccines, such as those for mumps and rubella (MMR) and for mumps, rubella, and varicella (MMR-V).
The recommended age of first vaccination varies from 6 to 15 months and represents a balance between the optimal age for seroconversion and the probability of acquiring measles before that age. The proportions of children who develop protective levels of antibody after measles vaccination approximate 85% at 9 months of age and 95% at 12 months. Common childhood illnesses concomitant with vaccination may reduce the level of immune response, but such illness is not a valid reason to withhold vaccination. Measles vaccines have been well tolerated and immunogenic in HIV-1-infected children and adults, although antibody levels may wane. Because of the potential severity of wild-type measles virus infection in HIV-1-infected children, routine measles vaccination is recommended except for those who are severely immunocompromised. Measles vaccination is contraindicated in individuals with other severe deficiencies of cellular immunity because of the possibility of disease due to progressive pulmonary or CNS infection with the vaccine virus.
The duration of vaccine-induced immunity is at least several decades if not longer. Rates of secondary vaccine failure 10–15 years after immunization have been estimated at ~5% but are probably lower when vaccination takes place after 12 months of age. Decreasing antibody concentrations do not necessarily imply a complete loss of protective immunity: a secondary immune response usually develops after reexposure to measles virus, with a rapid rise in antibody titers in the absence of overt clinical disease.
Standard doses of currently licensed measles vaccines are safe for immunocompetent children and adults. Fever to 39.4°C (103°F) occurs in ~5% of seronegative vaccine recipients, and 2% of vaccine recipients develop a transient rash. Mild transient thrombocytopenia has been reported, with an incidence of ~1 case per 40,000 doses of MMR vaccine.
Since the publication of a report in 1998 hypothesizing that MMR vaccine may cause a syndrome of autism and intestinal inflammation, much public attention has focused on this purported association. The events that followed publication of this report led to diminished vaccine coverage in the United Kingdom and provide important lessons in the misinterpretation of epidemiologic evidence and the communication of scientific results to the public. The publication that incited the concern was a case series describing 12 children with a regressive developmental disorder and chronic enterocolitis; 9 of these children had autism. In 8 of the 12 cases, the parents associated onset of the developmental delay with MMR vaccination. This simple temporal association was misinterpreted and misrepresented as a possible causal relationship, first by the lead author of the study and then by elements of the media and the public. Subsequently, several comprehensive reviews and additional epidemiologic studies refuted evidence of a causal relationship between MMR vaccination and autism.