Measles Open Access

Measles is an acute viral disease characterized by fever, cough, coryza, and conjunctivitis, followed by a maculopapular rash beginning on the face and spreading cephalocaudally and centrifugally. During the prodromal period, a pathognomonic enanthema,(Koplik spots) may be present. Complications of measles, including otitis media, bronchopneumonia, laryngotracheobronchitis (croup), and diarrhea, occur commonly in young children and immunocompromised hosts. Acute encephalitis, which often results in neurologic deficits, occurs in approximately 1 of every 1000 cases. In the postelimination era in the United States, death, predominantly resulting from respiratory and neurologic complications, has occurred in 1 to 3 of every 1000 cases reported. Case fatality rates are increased in children younger than 5 years, pregnant people, and immunocompromised children, including children with leukemia, human immunodeficiency virus (HIV) infection, and severe malnutrition (including vitamin A deficiency). Sometimes the characteristic rash does not develop in immunocompromised patients.

Measles inclusion body encephalitis (MIBE) is a rare manifestation of measles infection in immunocompromised individuals usually presenting within 1 year of measles infection. Disease onset is subacute with progressive neurologic dysfunction occurring over weeks to months. Subacute sclerosing panencephalitis (SSPE) is a rare degenerative central nervous system disease characterized by behavioral and intellectual deterioration and seizures that generally occurs 7 to 11 years after wild-type measles virus infection. The highest rates occur in children infected before 2 years of age.

Several recent studies suggest that children who have had measles have blunted immune responses to other pathogens and increased mortality for several years after infection. This has been attributed to measles-induced suppression of cell-mediated immune function leading to immune amnesia and susceptibility to previously encountered antigens, including vaccine antigens. This effect is another reason why measles prevention is so important.

Measles virus is an enveloped RNA virus with 1 serotype, classified as a member of the genus Morbillivirus in the Paramyxoviridae  family.

The only natural host of measles virus is humans. Measles virus is transmitted by direct contact with infectious droplets or by airborne spread. Measles is one of the most highly communicable of all infectious diseases; the attack rate in a susceptible individual exposed to measles is 90% in close-contact settings. Population immunity as high as 95% or greater is often needed to stop ongoing transmission. In temperate areas, the peak incidence of infection usually occurs during late winter and spring. In the prevaccine era, most cases of measles in the United States occurred in preschool- and young school-aged children, and few people remained susceptible by 20 years of age. Following implementation of routine childhood vaccination in the United States at 12 to 15 months of age, measles occurred more often in infants younger than 1 year and in older adolescents and adults who had not been adequately vaccinated. Infant susceptibility increases around the time when transplacentally acquired antibodies are no longer present. The childhood and adolescent immunization program in the United States began with licensure of the measles vaccine in 1963 and has resulted in a greater than 99% decrease in the reported incidence of measles, with declaration of measles elimination (ie, absence of endemic measles transmission for more than 1 year) in 2000.

From 1989 to 1991, the incidence of measles in the United States increased because of low immunization rates in preschool-aged children, especially in urban areas, and because of primary vaccine failures in children who had received 1 measles-containing vaccine dose. Following improved coverage in preschool-aged children and implementation of a routine second dose of measles, mumps, and rubella (MMR) vaccine for children, the incidence of measles has declined to extremely low levels (<1 case per 1 million population). Unfortunately, increasing numbers of cases and outbreaks of measles have occurred in many states in more recent years. The majority of these cases are linked to importation of measles by nonvaccinated international United States travelers from countries where measles is endemic, including countries in Western Europe, and subsequent internal spread among unimmunized subpopulations, including intentionally unimmunized children.

Progress continues toward global control and regional measles elimination, with a 94% drop in estimated measles deaths worldwide between 2000 and 2020.¹⁵⁵  By the end of 2021, 76 countries had been verified by independent regional commissions as having achieved or maintained measles elimination status. However, none of the World Health Organization (WHO) regions had achieved and sustained elimination, and no African Region country has yet been verified to have eliminated measles. WHO’s Region of the Americas achieved verification of measles elimination in 2016; however, endemic measles transmission was reestablished in Venezuela (2016) and Brazil (2018).

Estimated coverage of first dose of measles-containing vaccine decreased from 86% in 2019 to 84% in 2020 and 81% in 2021 during the COVID-19 pandemic.¹⁵⁶  Worsening of suboptimal surveillance coupled with increased population susceptibility attributable to vaccine hesitancy and decreased routine vaccination during the COVID-19 pandemic remain major threats to global elimination of measles.

Lack of response to vaccine (ie, primary vaccine failure) occurs in as many as 7% of people who receive a single dose of measles-containing vaccine at 12 months or older. Most cases of measles in previously immunized children are attributable to primary vaccine failures, but waning immunity after immunization (ie, secondary vaccine failure) may be a factor in some cases. Primary vaccine failure was the main reason that in 1989 a 2-dose vaccine schedule was recommended routinely for children and high-risk adults.¹⁵⁷ 

Patients infected with wild-type measles virus are contagious from 4 days before the rash through 4 days after appearance of the rash. Immunocompromised patients who may have prolonged excretion of the virus in respiratory tract secretions can be contagious for the duration of the illness. Patients with SSPE are not contagious.

The incubation period averages 11 to 12 days from exposure to onset of prodromal symptoms, and the average interval between exposure and appearance of rash is 14 days, with a range of 7 to 21 days. In SSPE, the mean incubation period of 84 cases reported between 1976 and 1983 was 10.8 years.

Measles virus infection can be confirmed by: (1) detection of measles viral RNA by nucleic acid amplification test (NAAT); (2) detection of measles virus-specific immunoglobulin (Ig) M; (3) a fourfold increase in measles IgG antibody concentration in paired acute and convalescent serum specimens (collected at least 10 days apart); or (4) isolation of measles virus in cell culture. Detection of IgM in serum samples by enzyme immunoassay has been the preferred method for case confirmation; however, as the incidence of disease decreases, the positive predictive value of IgM detection decreases. For this reason, detection of viral RNA in throat, nasal, and posterior nasopharyngeal swab specimens; bronchial lavage samples; blood or urine samples (respiratory samples are preferred specimens, and sampling more than 1 site may increase sensitivity) is playing an increasing role in case confirmation. A serum sample as well as a throat swab specimen should be obtained from any patient in whom measles is suspected. Many state public health laboratories, the Association of Public Health Laboratories Vaccine Preventable Disease Reference Centers (VPD-RCs), and the Measles Laboratory at the Centers for Disease Control and Prevention (CDC) can perform reverse transcriptase polymerase chain reaction (RT-PCR) assays to detect measles RNA. Isolation of measles virus in cell culture is not recommended for routine case confirmation, because isolation can take up to 2 weeks to complete.

The sensitivity of measles IgM assays varies by timing of specimen collection, immunization status of the patient, and the assay method itself. Up to 20% of assays for IgM may have a false-negative result in the first 72 hours after rash onset. If the measles IgM result is negative and the patient has a generalized rash lasting more than 72 hours, the measles IgM test should be repeated. Measles IgM is detectable for at least 1 month after rash onset in unimmunized people but might be absent or present only transiently in people immunized with 1 or 2 measles-containing vaccine doses. Therefore, a negative IgM test result should not be used to rule out the diagnosis in immunized people.

Detection of viral RNA by NAAT provides a rapid and sensitive method for case confirmation. It is important to collect samples for RNA detection as soon as possible after rash onset, because viral shedding declines with time after rash. Specimen timing and quality greatly influence the results of NAATs, so a negative result should not be the only criterion used to rule out a case of measles. Another advantage of collecting samples for molecular detection of the virus is that these samples can also be used to genotype the virus, which is important to determine patterns of importation and transmission.

In populations with high rates of measles-containing vaccine coverage, such as those in the United States, comprehensive serologic and virologic testing generally is not available locally and requires submitting specimens to state public health laboratories or the CDC. Individuals with a febrile rash illness who are seronegative for measles IgM and have negative NAAT results for measles should be tested for rubella using the same specimens.

No specific antiviral therapy is available. Measles virus is susceptible in vitro to ribavirin, which has been administered by the intravenous and aerosol routes to treat severely affected and immunocompromised children with measles. However, no controlled trials have been conducted, and ribavirin is not licensed by the US Food and Drug Administration for treatment of measles. Intravenous ribavirin is available only from the manufacturer through an emergency investigational new drug (eIND) application.

The WHO currently recommends vitamin A for all children with measles, regardless of their country of residence. Many US experts concur with administering vitamin A to all children in the United States with measles, regardless of hospitalization status. Vitamin A treatment of children with measles in resource-limited countries has been associated with decreased morbidity and mortality rates. Low serum concentrations of vitamin A also have been found in children in the United States, and children with more severe measles illness may have lower vitamin A concentrations. Vitamin A for treatment of measles is administered once daily for 2 days (ie, immediately on diagnosis and repeated the next day), at the following doses:

• 200 000 IU (60 000 μg retinol activity equivalent [RAE]) for children 12 months or older;

• 100 000 IU (30 000 μg RAE) for infants 6 through 11 months of age; and

• 50 000 IU (15 000 μg RAE) for infants younger than 6 months.

• An additional (ie, a third) age-specific dose of vitamin A should be given 2 through 6 weeks later to children with clinical signs and symptoms of vitamin A deficiency.

In addition to standard precautions, airborne transmission precautions are indicated for 4 days after the onset of rash in otherwise healthy children and for the duration of illness in immunocompromised patients. Exposed susceptible patients should be placed on airborne precautions for 21 days after last exposure (28 days if the patient received immune globulin as postexposure prophylaxis).¹⁵⁸ 

Evidence of immunity to measles includes any of the following:

1. Documentation of age-appropriate vaccination with a live measles-containing vaccine:

   • Preschool-aged children: 1 dose administered after the first birthday;

   • School-aged children (grades K–12): 2 doses; the first dose administered after the first birthday and the second dose administered at least 28 days after the first dose;

   • Adults not at high risk: 1 dose administered after the first birthday;

   • Adults at high risk (eg, students in postsecondary education institutions, health care workers, international travelers): 2 doses; the first dose administered after the first birthday and the second dose administered at least 28 days after the first dose;

2. Laboratory evidence of immunity;

3. Laboratory confirmation of disease; or

4. Born before 1957.

Table 3.32 and Table 3.33 summarize the use of vaccine and immune globulin (IG) for postexposure prophylaxis in people who are not immunocompromised or pregnant and people who are immunocompromised or pregnant, respectively.

Available data suggest that measles vaccine, if administered within 72 hours of measles exposure to susceptible individuals, will provide protection or disease modification in some cases. Measles-containing vaccine should be considered in all exposed individuals who are vaccine eligible and who have not been vaccinated or have received only 1 dose of vaccine (the second measles vaccine dose can be administered ≥28 days after the first measles vaccine dose). If the exposure does not result in infection, the vaccine should induce protection against subsequent measles exposures. Immunization is the intervention of choice for control of measles outbreaks in schools and child care centers and for vaccine-eligible people 12 months and older and has been used starting at 6 months of age with good efficacy in previous measles epidemics in the United States.

Either immune globulin intramuscular (IGIM) or immune globulin intravenous (IGIV) can be administered within 6 days of exposure to prevent or modify measles in people who do not have evidence of measles immunity. Concentrations of measles antibodies in IGIM or IGIV products produced internationally may be different from those of products available in the United States. The recommended dose of IGIM is 0.50 mL/kg (maximum 15 mL). IGIV is the recommended IG preparation for pregnant people without evidence of measles immunity and for severely immunocompromised hosts, regardless of immunologic or vaccination status, including patients with severe primary immunodeficiency; patients who have received a hematopoietic cell transplant, until at least 12 months after finishing all immunosuppressive treatment or longer in patients who have developed graft-versus-host disease; patients undergoing treatment for acute lymphoblastic leukemia, within and until at least 6 months after completion of immunosuppressive chemotherapy; people who have received a solid organ transplant; people with human immunodeficiency virus (HIV) infection who have severe immunosuppression (for people ≤5 years of age, defined as a CD4+ T-lymphocyte percentage <15%; for people >5 years of age, defined as a CD4+ T-lymphocyte percentage <15% or a CD4+ T-lymphocyte count <200 lymphocytes/mm³); and patients younger than 12 months whose birthing parent received biologic response modifiers during pregnancy.^160,161  IGIV is recommended for these people because they may be at higher risk of severe measles and complications. IGIV also is recommended for people who weigh >30 kg, who would receive less than the recommended dose with IGIM preparations since the maximum volume administered is 15 mL. IGIV is administered at a dose of 400 mg/kg. For patients who already are receiving IGIV at regularly scheduled intervals, the usual dose of 400 mg/kg should be adequate for measles prophylaxis after exposures occurring within 3 weeks of receiving IGIV. For people routinely receiving immune globulin subcutaneous (IGSC) therapy, consult the prescribing information for specific dosing related to measles, because it may vary based on other product characteristics. IG is not indicated for household or other close contacts who have received 1 dose of vaccine at 12 months or older unless they are severely immunocompromised (as defined previously).

For children who receive IGIM for modification or prevention of measles after exposure, measles vaccine (if not contraindicated) should be administered 6 months after IGIM administration and 8 months after IGIV administration, provided the child is at least 12 months of age. Intervals vary between administration of other biologic products and measles-containing vaccines (see Table 1.11, p 69).

Children living with HIV who are exposed to measles require prophylaxis based on immune status and measles vaccine history. Children living with HIV with no to moderate immunosuppression who have evidence of immunity (eg, serologic evidence of immunity to measles or who received 2 doses of measles vaccine after initiation of ART) do not require any additional measures to prevent measles following an exposure. Mildly or moderately immunocompromised people living with HIV without evidence of immunity to measles (eg, no serologic evidence of immunity to measles and who have not received 2 doses of measles vaccine after initiation of ART) should receive immune globulin intramuscular (IGIM) at a dose of 0.5 mL/kg (maximum 15 mL). Severely immunocompromised hosts (for people ≤5 years of age, defined as a CD4+ T-lymphocyte percentage <15%; for people >5 years of age, defined as a CD4+ T-lymphocyte percentage <15% or a CD4+ T-lymphocyte count <200 lymphocytes/mm³) who are exposed to measles should receive immune globulin intravenous (IGIV) prophylaxis, 400 mg/kg, after exposure to measles, regardless of prior vaccination status, because they may not be protected by the vaccine. Children living with HIV who have received IGIV within 3 weeks of exposure do not require additional passive immunization.

To decrease health care-associated infection, immunization programs should be established to ensure that all people who work or volunteer in health care facilities (including students) have presumptive evidence of immunity to measles (see Immunization in Health Care Personnel, p 115).

The only measles vaccines licensed in the United States are live attenuated strains. Measles-containing vaccines provided through the Expanded Programme on Immunization in resource-limited countries meet the WHO standards and usually are comparable with the vaccines available in the United States. Measles vaccine is only available in the United States as combination formulations, which include MMR (M-M-R II, manufactured by Merck; and Priorix, manufactured by GSK) and measles, mumps, rubella, and varicella (MMRV [ProQuad], manufactured by Merck) vaccines; single-antigen measles vaccine no longer is available in the United States. Measles-containing vaccine in a dose of 0.5 mL can be administered subcutaneously or intramuscularly, depending on the specific vaccine formulation used; M-M-R II and MMRV can be given either subcutaneously or intramuscularly, while Priorix can be given only subcutaneously. Measles-containing vaccine can be administered simultaneously with other immunizations in a separate syringe at a separate site (see Simultaneous Administration of Multiple Vaccines, p 63).

Serum antimeasles antibodies develop in approximately 95% of children immunized at 12 months of age and 98% of children immunized at 15 months of age. Protection conferred by a single dose is durable in most people. A small proportion (5% or less) of immunized people may lose protection after several years. For measles elimination, 2 doses of measles-containing vaccine are required. More than 99% of people who receive 2 doses (separated by at least 28 days, and the first dose administered on or after the first birthday) develop serologic evidence of measles immunity. The second dose provides protection to those failing to respond to their primary measles immunization and, therefore, is not a booster dose. Immunization is not deleterious for people who already are immune. Immunized people do not transmit measles vaccine virus.

Improperly stored vaccine may fail to protect against measles. Since 1979, an improved stabilizer has been added to the vaccine that makes it more resistant to heat inactivation. For recommended storage of MMR and MMRV vaccines, see the manufacturers’ package labels. MMRV vaccine must be stored frozen between –58°F and +5°F.

The first dose of MMR vaccine should be administered at 12 through 15 months of age. Delays in administering the first dose contributed to large outbreaks in the United States from 1989 to 1991. The second dose is recommended routinely at school entry (ie, 4 through 6 years of age) but can be administered at an earlier age (eg, during an outbreak or before international travel) provided the interval between the first and second MMR doses is at least 28 days. Catch-up second-dose immunization should occur for all school-aged children (elementary, middle, high school) who have received only 1 dose, including at the adolescent visit at 11 through 12 years of age and older. If a child receives a dose of measles vaccine before 12 months of age, this dose is not counted toward the required number of doses; the universally recommended 2 doses are still required in the United States beginning at 12 through 15 months of age and separated by at least 28 days.

• MMRV vaccine is indicated for simultaneous immunization against measles, mumps, rubella, and varicella among children 12 months through 12 years of age; MMRV vaccine is not indicated for people outside this age group. See Varicella-Zoster Infections, p 938, for recommendations for use of MMRV vaccine for the first dose.

• Children with HIV infection should not receive MMRV vaccine because of lack of safety data of the quadrivalent vaccine in children infected with HIV.

• MMRV vaccine may be administered with other vaccines recommended at 12 through 15 months of age or at 4 through 6 years of age (www.publications.aap.org/redbook/resources/15585/).

• At least 28 days should elapse between a dose of measles-containing vaccine, such as MMR vaccine, and a dose of MMRV vaccine. However, the recommended minimal interval between 2 separate MMRV vaccine doses is 90 days.

Colleges and other postsecondary educational institutions should require that all entering students have documentation of evidence of measles immunity (see Evidence of Immunity to Measles, p 574). Students without documentation of measles immunity should receive MMR vaccine on entry, followed by a second dose 28 days later, if not contraindicated.

During an outbreak, MMR vaccine should be offered to all vaccine-eligible people exposed or in the outbreak setting who lack evidence of measles immunity. During a community-wide outbreak that affects infants, MMR vaccine has been shown to be efficacious and may be recommended for infants 6 through 11 months of age (see Outbreak Control, p 585). Doses received prior to the first birthday do not count toward the recommended 2-dose series.

People traveling internationally (any country outside of the United States) should be immune to measles prior to travel. Infants 6 through 11 months of age should receive 1 dose of MMR vaccine at least 2 weeks before departure if possible, and then should receive a second dose of measles-containing vaccine at 12 through 15 months of age (at least 28 days after the initial measles immunization) and a third dose at 4 through 6 years of age. Children 12 months or older as well as adults who have received 1 dose and are traveling to areas where measles is endemic or epidemic should receive their second dose before departure, provided the interval between doses is 28 days or more.

The US Department of State requires that internationally adopted children 10 years and older receive MMR vaccine before entry into the United States. Internationally adopted children who are younger than 10 years are exempt from Immigration and Nationality Act regulations pertaining to immunization of immigrants before arrival in the United States (see Children Who Received Immunizations Outside the United States or Whose Immunization Status is Unknown or Uncertain, p 119); adoptive parents are required to sign a waiver indicating their intention to comply with US immunization recommendations after their child’s arrival in the United States.

Adequate presumptive evidence of immunity to measles for people who work in health care facilities is: (1) documented administration of 2 doses of live-virus measles vaccine with the first dose administered at ≥12 months of age and the second dose at least 28 days after the first; (2) laboratory evidence of immunity or laboratory confirmation of disease; or (3) birth before 1957. Birth before 1957 is not a guarantee of measles immunity, and therefore, facilities should consider vaccinating unimmunized personnel born before 1957 who lack laboratory evidence of immunity with 2 doses of MMR vaccine at the appropriate interval (see Immunization in Health Care Personnel, p 115). For recommendations during an outbreak, see Outbreak Control (p 585).

A body temperature of 39.4°C (103°F) or higher develops in approximately 5% to 15% of vaccine recipients, usually between 5 and 12 days after receipt of MMR vaccine; fever generally lasts 1 to 2 days but may last as long as 5 days. Most people with fever do not have other symptoms. Transient rashes have been reported in approximately 5% of vaccine recipients. Although recipients who develop fever and/or rash are not considered contagious and are not at risk for long-term sequelae of measles, suspicion for wild-type measles may be high, especially if vaccine was administered as part of an outbreak response. Therefore, rapid differentiation of vaccine reactions from infections with wild-type virus is critical for guiding the public health response to outbreaks. Vaccine reactions can be laboratory confirmed by detecting measles vaccine virus in respiratory secretions or urine followed by sequencing to determine genotype or by use of a NAAT for specific detection of measles vaccine strains (MeVa) that is available at the CDC and through state health departments.

Febrile seizures 5 to 12 days after immunization occur in 1 in 3000 to 4000 people immunized with MMR vaccine. Transient thrombocytopenia occurs in 1 in 22 000 to 40 000 people after administration of measles-containing vaccines, specifically MMR (see Thrombocytopenia, p 583). There is no evidence that reimmunization increases the risk of adverse events in people already immune to these diseases. Data indicate that only people who are not immune to the viruses in MMR tend to have adverse effects. Thus, events following a second dose of MMR vaccine would be expected to be substantially lower than after a first dose because most people who received a first dose would be immune.

Rates of most local and systemic adverse events for children immunized with MMRV vaccine are comparable with rates for children immunized with MMR and varicella vaccines administered concomitantly. However, recipients of a first dose of MMRV vaccine have a greater rate of fever 102°F (38.9°C) or higher than do recipients of MMR and varicella vaccine administered concomitantly (22% vs 15%, respectively). Febrile seizures occur in 1 in 1100 to 1400 children immunized with a first dose of MMRV vaccine at 12 through 23 months of age and in 1 in 2500 to 3000 children immunized with a first dose of MMR and varicella vaccines administered separately at the same visit. The period of risk for febrile seizures is from 5 to 12 days following receipt of the vaccine. The benefit of using MMRV instead of MMR and monovalent varicella vaccines separately is that the quadrivalent product results in 1 fewer injection. Either MMRV or separate MMR and varicella vaccines are an acceptable option for dose 1 at 12 through 15 months of age and pediatricians should discuss risks and benefits of the vaccine choices with the parents or caregivers. For the first dose of measles, mumps, rubella, and varicella vaccines at ages 48 months and older and for dose 2 at any age (15 months through 12 years), use of MMRV vaccine generally is preferred over separate injections of MMR and varicella vaccines to minimize the number of injections.

The reported frequency of central nervous system conditions, such as encephalitis and encephalopathy, after measles immunization is less than 1 per million doses administered in the United States. Because the incidence of encephalitis or encephalopathy after measles immunization in the United States is lower than the observed incidence of encephalitis of unknown cause, some or most of the rare reported severe neurologic disorders may be related temporally, rather than causally, to measles immunization. Multiple studies, as well as the National Academy of Medicine Vaccine Safety Review, refute a causal relationship between autism and MMR vaccine or between inflammatory bowel disease and MMR vaccine.

Children with minor illnesses, such as upper respiratory tract infections, may be immunized. Fever is not a contraindication to immunization. However, if other manifestations suggest a more serious illness, immunization should be deferred until the illness has resolved.

Hypersensitivity reactions occur rarely and usually are minor, consisting of wheal-and-flare reactions or urticaria at the injection site. Reactions have been attributed to trace amounts of neomycin or gelatin or some other component in the vaccine formulation. Anaphylaxis is rare. Measles vaccine is produced in chicken embryo cell culture and does not contain significant amounts of egg white (ovalbumin) cross-reacting proteins. Children with egg allergy are at low risk of anaphylactic reactions to measles-containing vaccine (including MMR and MMRV). Skin testing of children for egg allergy is not predictive of reactions to MMR vaccine and is not recommended before administering MMR or other measles-containing vaccine. People with allergies to chickens or feathers are not at increased risk of reaction to the vaccine.

Measles-containing vaccine should not be administered to people who have had a severe allergic reaction to a previous dose of measles-containing vaccine or to a vaccine component.

Rarely, MMR vaccine can be associated with mild thrombocytopenia within 2 months of immunization, with a temporal clustering 2 to 3 weeks after immunization. Most cases of thrombocytopenia resolve within 1 week. Based on case reports, the risk of vaccine-associated thrombocytopenia may be higher for people who previously experienced thrombocytopenia, especially if it occurred in temporal association with earlier MMR immunization. The decision to immunize these children should be based on assessment of immunity after the first dose and the benefits of protection against measles, mumps, and rubella in comparison with the risks of recurrence of thrombocytopenia after immunization. The risk of thrombocytopenia is higher after the first dose of vaccine than after the second dose. There have been no reported cases of thrombocytopenia associated with receipt of MMR vaccine that have resulted in hemorrhagic complications or death in otherwise healthy people.

IG preparations interfere with the serologic response to measles vaccine for variable periods, depending on the dose of IG administered. Suggested intervals between IG or blood-product administration and measles immunization are provided in Table 1.11 (p 69). If vaccine is administered at intervals shorter than those indicated, as may be warranted if the risk of exposure to measles is imminent, the child should be reimmunized at or after the appropriate interval for immunization (and at least 28 days after the earlier immunization).

MMR vaccine should be administered at least 2 weeks before planned administration of IG, blood transfusion, or other blood products because of the theoretical possibility that antibody in those products could neutralize vaccine virus and interfere with successful immunization. If IG must be administered within 14 days after administration of MMR or MMRV, these vaccines should be administered again after the interval specified in Table 1.11 (p 69).

Tuberculin skin testing or interferon gamma release assay (IGRA) testing is not a prerequisite for MMR immunization. Antituberculosis therapy should be initiated before administering MMR vaccine to people with untreated tuberculosis infection or disease. Tuberculin skin or IGRA testing, if otherwise indicated, can be performed on the day of immunization with MMR vaccine. Otherwise, tuberculin skin or IGRA testing should be postponed for 4 to 6 weeks, because measles immunization temporarily may suppress tuberculin skin test reactivity and possibly affect IGRA testing.

Immunocompromised patients with disorders associated with increased severity of viral infections should not receive live-virus measles vaccine (the exception is people with HIV infection, unless they have evidence of severe immunosuppression; see Immunization and Other Considerations in Immunocompromised Children, p 93, and HIV Infection, below). The risk of exposure to measles for immunocompromised patients can be decreased by immunizing their close susceptible contacts. Immunized people do not shed or transmit infectious measles vaccine virus. Management of immunodeficient and immunosuppressed patients exposed to measles can be facilitated by previous knowledge of their immune status. If possible, children should receive measles vaccine before initiating treatment with biologic response modifiers, such as tumor necrosis factor antagonists, and before transplantation, ideally with 2 doses. Severely immunocompromised patients should receive IG after measles exposure regardless of immunologic or vaccination status (see Care of Exposed People, p 574, Table 3.32, and Table 3.33).

For patients who have received high doses of corticosteroids (≥2 mg/kg of body weight or ≥20 mg/day of prednisone or its equivalent for people who weigh ≥10 kg) for 14 days or more and who otherwise are not immunocompromised, the recommended interval between stopping the corticosteroids and immunization is at least 4 weeks (see Immunization and Other Considerations in Immunocompromised Children, p 93). In general, inhaled steroids do not cause immunosuppression and are not a contraindication to measles immunization.

Measles immunization (administered as MMR vaccine) is recommended for all people ≥12 months of age with HIV who do not have evidence of measles immunity and who do not have evidence of severe immunosuppression, because measles can be severe and sometimes is fatal in patients with HIV (see Human Immunodeficiency Virus Infection, p 489). For vaccination purposes, severe immunosuppression for people ≤5 years of age is defined as a CD4+ T-lymphocyte percentage <15%, and for people >5 years of age is defined as a CD4+ T-lymphocyte percentage <15% or a CD4+ T-lymphocyte count <200 lymphocytes/mm³. Severely immunocompromised HIV-infected infants, children, adolescents, and young adults should not receive measles virus-containing vaccine. MMRV vaccine should not be administered to any infant or child with HIV, regardless of degree of immunosuppression, because of lack of safety data in this population. Children, adolescents, and adults with newly diagnosed HIV and without evidence of measles immunity should complete a 2-dose schedule with MMR vaccine as soon as possible after diagnosis, unless they have evidence of severe immunosuppression. People with perinatally acquired HIV who were vaccinated against measles prior to the establishment of effective ART should be considered unvaccinated and should be revaccinated with 2 doses of MMR vaccine once effective ART has been administered, unless they have other acceptable current evidence of measles immunity or unless they are severely immunocompromised. All members of the household of an HIV-infected person who lack evidence of measles immunity should receive 2 doses of MMR.

Children with a personal or family history of seizures should be immunized after parents or guardians are advised that the risk of seizures after measles immunization is increased slightly. Children receiving anticonvulsants should continue such therapy after measles immunization.

Measles-containing vaccine should not be administered to people known to be pregnant. People who receive MMR vaccine should not become pregnant for at least 28 days. This precaution is based on the theoretical risk of fetal infection, which applies to administration of any live-virus vaccine to people who might be pregnant or who might become pregnant shortly after immunization. No data from people who were inadvertently vaccinated while pregnant substantiate this theoretical risk. When immunizing adolescents and young adults against measles, recommended precautions include asking if they are pregnant, excluding people who are pregnant, and explaining the theoretical risks to others who may become pregnant. Pregnancy testing prior to immunization is not required.

Every suspected measles case should be reported immediately to the local health department, and every effort must be made to obtain laboratory evidence that would confirm that the illness is measles, especially if the illness may be the first case in the community. Subsequent prevention of spread of measles depends on prompt immunization of people at risk of exposure or people already exposed. People who have not been immunized, including those who have been exempted from measles immunization for medical reasons, should be excluded from school, child care, and health care settings until at least 21 days after the onset of rash in the last case of measles involved in the outbreak.

During measles outbreaks in child care facilities, schools, and colleges and other institutions of higher education, all students, their siblings, and personnel born in 1957 or after who cannot provide evidence of measles immunity should be immunized. People receiving their second dose, as well as unimmunized people receiving their first dose as part of the outbreak-control program, may be readmitted immediately to the school or child care facility.

If an outbreak occurs in an area served by a hospital or within a hospital, all employees and volunteers who cannot provide evidence of immunity to measles should receive 2 doses of MMR vaccine. Because some health care personnel born before 1957 have acquired measles in health care facilities, immunization with 2 doses of MMR vaccine is recommended for health care personnel without serologic evidence of immunity in this age category during outbreaks. Serologic testing before immunization is not recommended during an outbreak because rapid immunization is required to halt disease transmission. Health care personnel without evidence of immunity who have been exposed should be relieved of direct patient contact from the fifth day after the first exposure to the 21^st day after the last exposure, regardless of whether they received vaccine or IG after the exposure. Health care personnel who become ill should be relieved of patient contact until 4 days after rash develops.