The vaccine is less effective in HIV-infected infants than in the general population, but early treatment with antiretroviral drugs can increase its effectiveness. Measles vaccination programs are often used to deliver other child health interventions as well, such as bed nets to protect against malaria, antiparasite medicine and vitamin A supplements, and so contribute to the reduction of child deaths from other causes.The Advisory Committee on Immunization Practices (ACIP) recommends that all adult international travelers who do not have positive evidence of previous measles immunity receive two doses of MMR vaccine before traveling, although birth before 1957 is presumptive evidence of immunity. Those born in the United States before 1957 are likely to have been naturally infected with measles virus and generally need not be considered susceptible.There have been false claims of an association between the measles vaccine and autism; this incorrect concern has reduced the rate of vaccination and increased the number of cases of measles where immunization rates became too low to maintain herd immunity. Additionally, there have been false claims that measles infection protects against cancer.Administration of the MMR vaccine may prevent measles after exposure to the virus (post-exposure prophylaxis). Post-exposure prophylaxis guidelines are specific to jurisdiction and population. Passive immunization against measles by an intramuscular injection of antibodies could be effective up to the seventh day after exposure. Compared to no treatment, the risk of measles infection is reduced by 83%, and the risk of death by measles is reduced by 76%.
Risk factors for measles virus infection include immunodeficiency caused by HIV or AIDS, immunosuppression following receipt of an organ or a stem cell transplant, alkylating agents, or corticosteroid therapy, regardless of immunization status; travel to areas where measles commonly occurs or contact with travelers from such an area; and the loss of passive, inherited antibodies before the age of routine immunization. Pathophysiology
Once the measles virus gets onto the mucosa, it infects the epithelial cells in the trachea or bronchi. Measles virus uses a protein on its surface called hemagglutinin (H protein), to bind to a target receptor on the host cell, which could be CD46, which is expressed on all nucleated human cells, CD150, aka signaling lymphocyte activation molecule or SLAM, which is found on immune cells like B or T cells, and antigen-presenting cells, or nectin-4, a cellular adhesion molecule. Once bound, the fusion, or F protein helps the virus fuse with the membrane and ultimately get inside the cell.As the virus is a single-stranded negative-sense RNA virus, it includes the enzyme RNA-dependent RNA polymerase (RdRp) which is used to transcribe its genome into a positive-sense mRNA strand.After entering a cell, it is ready to be translated into viral proteins, wrapped in the cells lipid envelope, and sent out of the cell as a newly made virus. Within days, the measles virus spreads through local tissue and is picked up by dendritic cells and alveolar macrophages, and carried from that local tissue in the lungs to the local lymph nodes.