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Subcutaneous injection is the means of measles vaccination. In the United States, the measles vaccine includes at least 1000 median tissue culture infective doses (TCID). Immunization can be in its monovalent form or in the MMR vaccine. Both routes are equally effective in inhibiting viral replication.(13)

Vaccination results in antibody titers that are less than those after natural infection. This reduction in antibody production does not preclude the individual from protection; after seroconversion, a secondary dose of the attenuated vaccine can endow the patient with lifelong protection.(18)

Dosage  and Vaccine Failure

Recent measles outbreaks throughout the world may be due to vaccine failure. Primary vaccine failure (PVF) occurs when the subject does not make detectable antibodies in response to the vaccination. Secondary vaccine failure (SVF) results when the subject initially makes detectable antibodies in response to vaccination but these titers fall with time.(7) For this reason, it is important to establish a strong sense of cell-mediated immunity with vaccination in order to maintain resistance over the long-term.

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Protection against measles necessitates vaccine administration at the appropriate age. Vaccine failure can result when passively acquired material antibodies neutralize the vaccine virus before the patient develops an immune response. The vaccine must also be administered at an age old enough when the chances for the material antibody neutralization are low but young enough to avoid the risks of infection. In the United States, most children are vaccinated between 12 to 15 months of age, and are revaccinated again before they begin grade school due to a waning of immunity or vaccine failure with the first dose. A second dose of the measles vaccine has shown to substantially enhance oneís immunity against infection.(14)

However, in the third world or underserved parts of the globe, some children are at high risk for catching measles. For this reason, WHO recommends that immunization should commence at an earlier age: the initial dose should be administered at six months while the second dose should follow at nine months. The decrease in the short-term window further minimizes the chances that the child will contract the disease due to vaccine failure.(22) Since measles is most fatal in this age group, such a measure may minimize measles-related morbidity.

Though incidences of measles have been dramatically reduced in the United States with the popularity of route vaccination, outbreaks in the 1980s have further enforced the two-dose immunization policy as well as encouraged further studies on measles vaccine strategies.(26) It is our hope that continued immunization and research will enable us to one day eradicate the virus.

Measles remains one of the major childhood killers -- accounting for more child deaths than any other vaccine-preventable disease.

--State of the World's Vaccines and Immunization (9)

Measles vaccine generally has the lowest coverage of all EPI vaccines for children.

Photo taken from WHO(9)

This vaccine produces both humoral and cell-mediated immune responses, both of which are similar to those induced via natural infection. Humoral responses appear to be the most effective in immunity; both serum and nasal secretions reveal levels of IgG, IgM, and IgA antibodies.(7) IgM antibodies first appear 3 to 4 weeks after vaccination but decline, only to be replaced by serum IgG antibodies. IgA antibodies are predominately found in the mucous. All these antibodies decline over time but can be boosted when the body is faced again with the vaccine or the wild virus.(18)

Cell-mediated responses, though in need of greater study, are exemplified by increased levels of lymphocyte stimulation. These responses usually become evident about three weeks following vaccination. T-cell responses can be characterized by an immediate Th1-type response and an eventual and sustained shift to a Th2-type response.(4)  Initially, infection induces increased activation of CD8⁺ T cells, evidenced through the augmented production of interleukin-2 and interferon-g. These cytotoxic T lymphocytes (CTLs) are particularly important for viral clearance. However, this increase is only transient; soon, we see increased and prolonged levels of interleukin-4, which activates CD4⁺ cells.(17) These lymphocytes are responsible for antibody production.

In revaccination of the virus, we do not see IgM production. IgG antibodies are detectable, reconfirming that the body has been pre-exposed to the virus.(22) These antibody titer boosts tend to be transient; cellular immunity, on the other hand, persists much longer.(13) Nevertheless, the vaccine accelerates the immune response against the virus, leading to prolonged immunity against the disease.