Journal of Vaccine Research 2024, Vol.14, No.6, 287-296 http://medscipublisher.com/index.php/jvr 288 vaccination rates high. The goal is to give a clear view of why the MMR vaccine remains a key part of protecting public health. 2 Mechanism of Action of the MMR Vaccine 2.1 Measles, mumps, and rubella Measles, mumps, and rubella are serious viral diseases, and each has its own symptoms. Measles usually starts with a high fever, cough, runny nose, and red, watery eyes. A red rash often appears a few days later, beginning on the face and then spreading over the body (Figure 1) (Destefano and Shimabukuro, 2019). Measles can cause problems like ear infections, diarrhea, pneumonia, and brain swelling (encephalitis). In some cases, these can lead to long-term health issues or death. Figure 1 Symptoms of measles in children (Adopted from Destefano and Shimabukuro, 2019) Image caption: a: Child with characteristic red, blotchy rash on third day of the measles rash; b: Koplik spots on the soft palate and oropharynx due to pre-eruptive measles on day 3 of the illness (Adopted from Destefano and Shimabukuro, 2019) Mumps often causes swollen, painful salivary glands under the ears or jaw. Other signs include fever, headache, muscle pain, tiredness, and loss of appetite. Some people may also develop meningitis, encephalitis, hearing loss, or swelling of the testicles or ovaries, which can sometimes lead to infertility (Di Pietrantonj et al., 2020). Rubella, or German measles, usually causes a mild fever, headache, and a rash that starts on the face and spreads to the body. It may also cause swollen lymph nodes, cough, or a runny nose. Rubella is often mild in children but very dangerous for pregnant women. If a woman gets rubella during pregnancy, it can cause serious birth defects like heart problems, hearing and vision loss, or developmental delays in the baby. The MMR vaccine works well to prevent these diseases and their complications. After the full vaccine doses, the protection rates are about 95%~96% for measles, 72%~86% for mumps, and 89% for rubella (Di Pietrantonj et al., 2020). 2.2 Basic mechanism of immune response The MMR vaccine helps the body build protection by teaching the immune system how to fight these viruses. The vaccine contains live but weakened forms of the measles, mumps, and rubella viruses. After the vaccine is given, the body reacts by making antibodies. These are special proteins that can block the viruses. The immune system also uses T cells, which help find and destroy infected cells. B cells, another type of immune cell, are the ones that produce the antibodies (Tischer and Gerike, 2000; Davidkin et al., 2008; Prymula et al., 2021; Jiang, 2024). Both the T cells (cellular immunity) and the B cells (humoral immunity) work together to protect the body. This strong immune response is what makes the MMR vaccine so effective against measles, mumps, and rubella. 2.3 Composition of the MMR vaccine The MMR vaccine contains live but weakened (attenuated) viruses for measles, mumps, and rubella. Each virus strain is chosen carefully to make sure the vaccine is both safe and effective. The measles part usually comes from the Edmonston-Zagreb strain. The mumps part uses the Jeryl Lynn strain, and the rubella part uses the RA 27/3 strain (Tischer and Gerike, 2000; Czajka et al., 2009; Bonanni et al., 2019).
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