Measles vaccine

Measles is [[Endemic (epidemiology)|common]] worldwide. Although it was declared eliminated from the U.S. in 2000, high rates of vaccination and excellent communication with those who refuse vaccination are needed to prevent outbreaks and sustain the elimination of measles.<ref name=Parker/> Of the 66 cases of measles reported in the U.S. in 2005, slightly over half were attributable to one unvaccinated teenager who became infected during a visit to Romania.<ref>{{cite journal | author = Centers for Disease Control and Prevention (CDC) | title = Measles--United States, 2005 | journal = MMWR. Morbidity and Mortality Weekly Report | volume = 55 | issue = 50 | pages = 1348–51 | date = December 2006 | pmid = 17183226 | url = https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5550a2.htm | archive-url = https://web.archive.org/web/20150313120119/http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5550a2.htm | url-status = live | archive-date = 13 March 2015 }}</ref> This individual returned to a community with many unvaccinated children. The resulting outbreak infected 34 people, mostly children and virtually all unvaccinated; three of them were hospitalized. The public health response required making almost 5,000 phone calls as part of [[contact tracing]], arranging and performing testing as needed, and arranging emergency vaccination for at-risk people who had had contact with this person.<ref name="Parker" /> Taxpayers and local healthcare organizations likely paid more than US$167,000 in direct costs to contain this one outbreak.<ref name="Parker" /> A major [[epidemic]] was averted due to high rates of vaccination in the surrounding communities.<ref name=Parker>{{cite journal | vauthors = Parker AA, Staggs W, Dayan GH, Ortega-Sánchez IR, Rota PA, Lowe L, Boardman P, Teclaw R, Graves C, LeBaron CW | title = Implications of a 2005 measles outbreak in Indiana for sustained elimination of measles in the United States | journal = The New England Journal of Medicine | volume = 355 | issue = 5 | pages = 447–55 | date = August 2006 | pmid = 16885548 | doi = 10.1056/NEJMoa060775 | doi-access = free }}</ref>

Measles is [[Endemic (epidemiology)|common]] worldwide. Although it was declared eliminated from the U.S. in 2000, high rates of vaccination and excellent communication with those who refuse vaccination are needed to prevent outbreaks and sustain the elimination of measles.<ref name=Parker/> Of the 66 cases of measles reported in the U.S. in 2005, slightly over half were attributable to one unvaccinated teenager who became infected during a visit to Romania.<ref>{{cite journal | author = Centers for Disease Control and Prevention (CDC) | title = Measles--United States, 2005 | journal = MMWR. Morbidity and Mortality Weekly Report | volume = 55 | issue = 50 | pages = 1348–51 | date = December 2006 | pmid = 17183226 | url = https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5550a2.htm | archive-url = https://web.archive.org/web/20150313120119/http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5550a2.htm | url-status = live | archive-date = 13 March 2015 }}</ref> This individual returned to a community with many unvaccinated children. The resulting outbreak infected 34 people, mostly children and virtually all unvaccinated; three of them were hospitalized. The public health response required making almost 5,000 phone calls as part of [[contact tracing]], arranging and performing testing as needed, and arranging emergency vaccination for at-risk people who had had contact with this person.<ref name="Parker" /> Taxpayers and local healthcare organizations likely paid more than US$167,000 in direct costs to contain this one outbreak.<ref name="Parker" /> A major [[epidemic]] was averted due to high rates of vaccination in the surrounding communities.<ref name=Parker>{{cite journal | vauthors = Parker AA, Staggs W, Dayan GH, Ortega-Sánchez IR, Rota PA, Lowe L, Boardman P, Teclaw R, Graves C, LeBaron CW | title = Implications of a 2005 measles outbreak in Indiana for sustained elimination of measles in the United States | journal = The New England Journal of Medicine | volume = 355 | issue = 5 | pages = 447–55 | date = August 2006 | pmid = 16885548 | doi = 10.1056/NEJMoa060775 | doi-access = free }}</ref>

When addressing the major U.S. measles outbreak in 2019, the [[Centers for Disease Control and Prevention]] stated that outbreaks are more likely in areas with pockets of unvaccinated residents.<ref>{{Cite web |last=Centers for Disease Control and Prevention |date=15 May 2021 |title=Measles cases and outbreaks |url=https://www.cdc.gov/measles/cases-outbreaks.html |access-date=1 April 2025 |website=web.archive.org |archive-date=15 May 2021 |archive-url=https://web.archive.org/web/20210515151956/https://www.cdc.gov/measles/cases-outbreaks.html |url-status=bot: unknown }}</ref> However, during the U.S. outbreak beginning in February 2025, the agency declined to publicize their updated expert assessment and forecasting model supporting this conclusion, thereby choosing not to alert clinicians and the public of being at specific risk in areas with low immunization rates.<ref>{{Cite web |last=Callahan |first=Patricia |date=28 March 2025 |title=The CDC buried a measles forecast that stressed the need for vaccinations |url=https://www.propublica.org/article/measles-vaccine-rfk-cdc-report |access-date=1 April 2025 |website=ProPublica |language=en}}</ref>

When addressing the major U.S. measles outbreak in 2019, the [[Centers for Disease Control and Prevention]] stated that outbreaks are more likely in areas with pockets of unvaccinated residents.<ref>{{Cite web |last=Centers for Disease Control and Prevention |date=15 May 2021 |title=Measles cases and outbreaks |url=https://www.cdc.gov/measles/cases-outbreaks.html |access-date=1 April 2025 |website=web.archive.org |archive-date=15 May 2021 |archive-url=https://web.archive.org/web/20210515151956/https://www.cdc.gov/measles/cases-outbreaks.html |url-status=dead }}</ref> However, during the U.S. outbreak beginning in February 2025, the agency declined to publicize their updated expert assessment and forecasting model supporting this conclusion, thereby choosing not to alert clinicians and the public of being at specific risk in areas with low immunization rates.<ref>{{Cite web |last=Callahan |first=Patricia |date=28 March 2025 |title=The CDC buried a measles forecast that stressed the need for vaccinations |url=https://www.propublica.org/article/measles-vaccine-rfk-cdc-report |access-date=1 April 2025 |website=ProPublica |language=en}}</ref>

The vaccine has [[non-specific effect of vaccines| nonspecific effects]] such as preventing respiratory infections, that may be greater than those of measles prevention alone.<ref>{{cite journal | vauthors = Mina MJ | title = Measles, immune suppression and vaccination: direct and indirect nonspecific vaccine benefits | journal = The Journal of Infection | volume = 74 | issue = Suppl 1 | pages = S10–S17 | date = June 2017 | pmid = 28646947 | doi = 10.1016/S0163-4453(17)30185-8 }}</ref><!-- <ref name=Sankoh2014/> --> These benefits are greater when the vaccine is given before one year of age.<ref>{{cite journal | vauthors = Nic Lochlainn LM, de Gier B, van der Maas N, van Binnendijk R, Strebel PM, Goodman T, de Melker HE, Moss WJ, Hahné SJ | title = Effect of measles vaccination in infants younger than 9 months on the immune response to subsequent measles vaccine doses: a systematic review and meta-analysis | language = English | journal = The Lancet. Infectious Diseases | volume = 19 | issue = 11 | pages = 1246–1254 | date = November 2019 | pmid = 31548081 | pmc = 6838663 | doi = 10.1016/S1473-3099(19)30396-2 }}</ref><!-- <ref name=Sankoh2014/> --> A high-[[Antibody titer|titre]] vaccine resulted in worse outcomes in girls, and consequently is not recommended by the World Health Organization.<ref name=Sankoh2014>{{cite journal | vauthors = Sankoh O, Welaga P, Debpuur C, Zandoh C, Gyaase S, Poma MA, Mutua MK, Hanifi SM, Martins C, Nebie E, Kagoné M, Emina JB, Aaby P | title = The non-specific effects of vaccines and other childhood interventions: the contribution of INDEPTH Health and Demographic Surveillance Systems | journal = International Journal of Epidemiology | volume = 43 | issue = 3 | pages = 645–653 | date = June 2014 | pmid = 24920644 | pmc = 4052142 | doi = 10.1093/ije/dyu101 }}</ref>

The vaccine has [[non-specific effect of vaccines| nonspecific effects]] such as preventing respiratory infections, that may be greater than those of measles prevention alone.<ref>{{cite journal | vauthors = Mina MJ | title = Measles, immune suppression and vaccination: direct and indirect nonspecific vaccine benefits | journal = The Journal of Infection | volume = 74 | issue = Suppl 1 | pages = S10–S17 | date = June 2017 | pmid = 28646947 | doi = 10.1016/S0163-4453(17)30185-8 }}</ref><!-- <ref name=Sankoh2014/> --> These benefits are greater when the vaccine is given before one year of age.<ref>{{cite journal | vauthors = Nic Lochlainn LM, de Gier B, van der Maas N, van Binnendijk R, Strebel PM, Goodman T, de Melker HE, Moss WJ, Hahné SJ | title = Effect of measles vaccination in infants younger than 9 months on the immune response to subsequent measles vaccine doses: a systematic review and meta-analysis | language = English | journal = The Lancet. Infectious Diseases | volume = 19 | issue = 11 | pages = 1246–1254 | date = November 2019 | pmid = 31548081 | pmc = 6838663 | doi = 10.1016/S1473-3099(19)30396-2 }}</ref><!-- <ref name=Sankoh2014/> --> A high-[[Antibody titer|titre]] vaccine resulted in worse outcomes in girls, and consequently is not recommended by the World Health Organization.<ref name=Sankoh2014>{{cite journal | vauthors = Sankoh O, Welaga P, Debpuur C, Zandoh C, Gyaase S, Poma MA, Mutua MK, Hanifi SM, Martins C, Nebie E, Kagoné M, Emina JB, Aaby P | title = The non-specific effects of vaccines and other childhood interventions: the contribution of INDEPTH Health and Demographic Surveillance Systems | journal = International Journal of Epidemiology | volume = 43 | issue = 3 | pages = 645–653 | date = June 2014 | pmid = 24920644 | pmc = 4052142 | doi = 10.1093/ije/dyu101 }}</ref>