The Resurgence of Measles, Mumps, and Pertussis

Abstract

•Every 20 seconds a child dies in the world from a vaccine-preventable disease (VPD).•Despite adequate vaccination rates, measles, mumps, and pertussis cases are on the rise in the United States.•Vaccine hesitancy, high contagiousness of VPDs, and safety are linked to the resurgence.•Early provider-parent communication and education are key to vaccine uptake. Although vaccines are one of the greatest scientific innovations to prevent disease and promote well-being, 1 in 10 children is not being vaccinated. This has directly contributed to the rise in vaccine-preventable diseases. Because of the high contagiousness of measles, mumps, and pertussis, innovative efforts are paramount to prevent disease outbreaks in the United States and worldwide. This article reviews measles, mumps, and pertussis; explains the resurgence of these vaccine-preventable diseases; and offers evidence-based solutions for increasing vaccination rates. Although vaccines are one of the greatest scientific innovations to prevent disease and promote well-being, 1 in 10 children is not being vaccinated. This has directly contributed to the rise in vaccine-preventable diseases. Because of the high contagiousness of measles, mumps, and pertussis, innovative efforts are paramount to prevent disease outbreaks in the United States and worldwide. This article reviews measles, mumps, and pertussis; explains the resurgence of these vaccine-preventable diseases; and offers evidence-based solutions for increasing vaccination rates. This CE learning activity is designed to augment the knowledge, skills, and attitudes of nurse practitioners and assist in their treatment decisions related to the most prominent vaccine-preventable diseases; the reasons for altering, delaying, or declining vaccines; and the appropriate educational measures needed to increase childhood vaccine rates.At the conclusion of this activity, the participant will be able to:A.Describe the leading reasons behind the recent measles, mumps, and pertussis outbreaksB.Evaluate the causes for altering, delaying, or declining childhood vaccinesC.Apply the appropriate educational techniques to increase childhood vaccine ratesThe authors, reviewers, editors, and nurse planners all report no financial relationships that would pose a conflict of interest.The authors do not present any off-label or non-FDA-approved recommendations for treatment.This activity has been awarded 1 Contact Hour of which 1.0 credit is in the area of Pharmacology. The activity is valid for CE credit until July 1, 2021. This CE learning activity is designed to augment the knowledge, skills, and attitudes of nurse practitioners and assist in their treatment decisions related to the most prominent vaccine-preventable diseases; the reasons for altering, delaying, or declining vaccines; and the appropriate educational measures needed to increase childhood vaccine rates. At the conclusion of this activity, the participant will be able to:A.Describe the leading reasons behind the recent measles, mumps, and pertussis outbreaksB.Evaluate the causes for altering, delaying, or declining childhood vaccinesC.Apply the appropriate educational techniques to increase childhood vaccine rates The authors, reviewers, editors, and nurse planners all report no financial relationships that would pose a conflict of interest. The authors do not present any off-label or non-FDA-approved recommendations for treatment. This activity has been awarded 1 Contact Hour of which 1.0 credit is in the area of Pharmacology. The activity is valid for CE credit until July 1, 2021. Vaccines are one of the greatest scientific inventions available to prevent illness and death.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar Despite countless vaccine advances over the past 6 decades, some parents continue to question the safety, benefits, and necessity of vaccines.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar Some choose to alter, delay, or decline childhood vaccines, negatively impacting herd immunity and allowing vaccine-preventable diseases (VPDs) to accelerate.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar The shift from “pro”-vaccine to “anti”-vaccine piques alarming concerns that decades of successful vaccine programs may be in jeopardy. Although vaccines prevent approximately 2.5 million pediatric deaths worldwide annually, the sad fact is that 1 child still dies every 20 seconds from a VPD.2US Centers for Disease Control and PreventionGlobal health security: Immunization. 2014.https://www.cdc.gov/globalhealth/security/immunization.htmDate accessed: December 10, 2018Google Scholar Measles, mumps, and pertussis resurgence will be reviewed, noting their impact both in the United States and worldwide. Causes for vaccine skepticism and innovative ideas to increase vaccine uptake will also be presented. In 1963, the measles vaccine was introduced to the US and has reduced measles cases by greater than 99%.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar Because of the high contagiousness of measles, unvaccinated individuals have up to a 90% chance of contracting it if they are exposed.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar A single dose of measles, mumps, rubella (MMR) vaccine is 95% effective, and 2 doses of MMR are 99% effective at preventing measles.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar Measles was considered practically eliminated in the US in 2000 with a median of 60 cases reported yearly between 2001 and 2012.3American Academy of PediatricsRed Book: 2018 Report on the Committee of Infectious Diseases. American Academy of Pediatrics, Itasca, IL2018Google Scholar In 2014, 23 outbreaks in 27 different states totaling 667 cases were reported, the largest annual disease burden in the US since 1994.4US Centers for Disease Control and PreventionMeasles cases and outbreaks. 2018.https://www.cdc.gov/measles/cases-outbreaks.htmlDate accessed: December 24, 2018Google Scholar The 2014 influx of measles cases began in an unvaccinated Amish congregation in Ohio infecting 383 people.4US Centers for Disease Control and PreventionMeasles cases and outbreaks. 2018.https://www.cdc.gov/measles/cases-outbreaks.htmlDate accessed: December 24, 2018Google Scholar The majority of the other cases reported in 2014 into 2015 were contracted at a Disneyland theme park imported from an index case from the Philippines.4US Centers for Disease Control and PreventionMeasles cases and outbreaks. 2018.https://www.cdc.gov/measles/cases-outbreaks.htmlDate accessed: December 24, 2018Google Scholar Analysis of the Disneyland outbreak concluded that 88% of the individuals infected were unvaccinated or had an unidentified vaccine status.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar In 2017, Minnesota experienced a measles outbreak that infected 65 individuals ranging from 3 months to 49 years of age.5Hall V. Banerjee E. Kenyon C. et al.Measles outbreak – Minnesota April–May 2017.MMWR Morb Mortal Wkly Rep. 2017; 66: 713-717Crossref PubMed Scopus (82) Google Scholar The outbreak was traced back to a 25-month-old hospitalized child who exposed over 8,200 people from 5 schools, 12 day care facilities, 3 health care centers, and many households.5Hall V. Banerjee E. Kenyon C. et al.Measles outbreak – Minnesota April–May 2017.MMWR Morb Mortal Wkly Rep. 2017; 66: 713-717Crossref PubMed Scopus (82) Google Scholar Ninety-five percent of the infected individuals were unvaccinated, and 31% required hospitalization for dehydration or pneumonia treatment.5Hall V. Banerjee E. Kenyon C. et al.Measles outbreak – Minnesota April–May 2017.MMWR Morb Mortal Wkly Rep. 2017; 66: 713-717Crossref PubMed Scopus (82) Google Scholar This outbreak shows how rapidly the measles virus spreads in a community lacking adequate vaccination and reinforces the need for continued education to prevent future outbreaks and hospitalizations. In October 2018, 17 children had confirmed cases of measles in Williamsburg, NY, and Borough Park, NY, and more than 40 cases were confirmed in the Jewish community of Rockland County, NY, from a child who visited Israel.6Hackett D.W. Israel launches measles vaccination program: measles outbreaks reported in London, Brooklyn, Rockland County, and Jerusalem. 2018.https://www.vaxbeforetravel.com/measles-outbreaks-reported-london-brooklyn-rockland-county-and-jerusalem%C2%A0Date accessed: December 10, 2018Google Scholar This led to a public health notice that any child within the Village of New Square school district who was undervaccinated or unvaccinated must be kept home 21 days after the last confirmed measles case.6Hackett D.W. Israel launches measles vaccination program: measles outbreaks reported in London, Brooklyn, Rockland County, and Jerusalem. 2018.https://www.vaxbeforetravel.com/measles-outbreaks-reported-london-brooklyn-rockland-county-and-jerusalem%C2%A0Date accessed: December 10, 2018Google Scholar This supports the importance of vaccine discussions at each and every patient visit and the need for continued laws regulating school vaccine requirements. As of December 1, 2018, 292 confirmed cases of measles from 16 different outbreaks involving 26 states and the District of Columbia have been reported in the US for the 2018 calendar year.4US Centers for Disease Control and PreventionMeasles cases and outbreaks. 2018.https://www.cdc.gov/measles/cases-outbreaks.htmlDate accessed: December 24, 2018Google Scholar This is more than double the cases from 2017 (120) and more than triple the cases from 2016 (86).4US Centers for Disease Control and PreventionMeasles cases and outbreaks. 2018.https://www.cdc.gov/measles/cases-outbreaks.htmlDate accessed: December 24, 2018Google Scholar The majority of the 2018 measles outbreaks have been in unvaccinated individuals exposed to international travelers.4US Centers for Disease Control and PreventionMeasles cases and outbreaks. 2018.https://www.cdc.gov/measles/cases-outbreaks.htmlDate accessed: December 24, 2018Google Scholar Europe is also experiencing the highest measles outbreak in over 2 decades secondary to suboptimal vaccination rates.7The New York Times Measles in Europe, recently at record low, jumps to highest level since 90’s. 2018.https://www.nytimes.com/2018/08/20/world/europe/europe-measles-cases.html?module=inlineDate accessed: November 30, 2018Google Scholar More than 41,000 cases of measles and 37 deaths have been reported in the first 6 months of 2018 in Europe.7The New York Times Measles in Europe, recently at record low, jumps to highest level since 90’s. 2018.https://www.nytimes.com/2018/08/20/world/europe/europe-measles-cases.html?module=inlineDate accessed: November 30, 2018Google Scholar Today, measles still infects 20 million people worldwide and is responsible for more than 89,000 deaths annually.8World Health Organization Measles. 2018.http://www.who.int/news-room/fact-sheets/detail/measlesDate accessed: October 1, 2018Google Scholar Through global vaccine initiatives from 2000 to 2017, the measles vaccine has prevented an estimated 21 million deaths.8World Health Organization Measles. 2018.http://www.who.int/news-room/fact-sheets/detail/measlesDate accessed: October 1, 2018Google Scholar Before the introduction of the mumps vaccine in the US in 1967, about 186,000 cases occurred annually in the US.9US Centers for Disease Control and PreventionMumps cases and outbreaks. 2018.https://www.cdc.gov/mumps/outbreaks.htmlDate accessed: December 24, 2018Google Scholar In 1989, the Advisory Committee on Immunization Practices recommended changing the MMR vaccine from 1 to 2 doses in response to multiple measles outbreaks. This resulted in a substantial reduction in mumps cases in the 1990s.10Marlin M. Marlow M. Moore K.L. et al.Recommendation of the advisory committee on immunization practices for use of a third dose of mumps virus-containing vaccine in persons at increased risk for mumps during an outbreak.MMWR Morb Mortal Wkly Rep. 2018; 67: 33-38Google Scholar However, between 2016 and 2017, mumps infected over 1.1 million people worldwide with over 12,000 of those cases within the US.11World Health Organization Mumps reported cases. 2018.http://apps.who.int/immunization_monitoring/globalsummary/timeseries/tsincidencemumps.htmlDate accessed: October 1, 2018Google Scholar Hundreds of college students from Iowa and Illinois were infected with the mumps in 2015/2016.9US Centers for Disease Control and PreventionMumps cases and outbreaks. 2018.https://www.cdc.gov/mumps/outbreaks.htmlDate accessed: December 24, 2018Google Scholar A close-knit community in Arkansas was affected with nearly 3,000 cases of mumps in 2016/2017.9US Centers for Disease Control and PreventionMumps cases and outbreaks. 2018.https://www.cdc.gov/mumps/outbreaks.htmlDate accessed: December 24, 2018Google Scholar Many outbreaks are noted in close-contact settings such as schools, colleges, sports teams, and camps.9US Centers for Disease Control and PreventionMumps cases and outbreaks. 2018.https://www.cdc.gov/mumps/outbreaks.htmlDate accessed: December 24, 2018Google Scholar As of December 1, 2018, there have been 2,106 cases of mumps in the US from 47 states and the District of Columbia.9US Centers for Disease Control and PreventionMumps cases and outbreaks. 2018.https://www.cdc.gov/mumps/outbreaks.htmlDate accessed: December 24, 2018Google Scholar When there are geographic pockets of children who are unvaccinated, VPDs, like mumps, can spread rapidly. After the introduction of the first pertussis vaccine in the 1940s, the US saw a decrease in pertussis cases, which lasted until 2004.12Kline N.P. Bartlett J. Fireman B. et al.Waning Tdap effectiveness in adolescents.Pediatrics. 2016; 137: 1-9Google Scholar However, since 2004, pertussis rates have steadily increased with a peak of 48,277 cases and 20 deaths reported in 2012.12Kline N.P. Bartlett J. Fireman B. et al.Waning Tdap effectiveness in adolescents.Pediatrics. 2016; 137: 1-9Google Scholar Although the acellular pertussis vaccine released in 1997 is considered safer, it wanes rapidly from the initial time of administration compared with the whole-cell pertussis vaccine used in the 1940s.13US Centers for Disease Control and PreventionPertussis cases by year (1922-2015). 2017.https://www.cdc.gov/pertussis/surv-reporting/cases-by-year.htmlDate accessed: October 5, 2018Google Scholar McGirr and Fisman14McGirr A. Fisman D.N. Duration of pertussis immunity after DTaP immunization: a meta-analysis.Pediatrics. 2015; 135: 331-343Crossref PubMed Scopus (120) Google Scholar found only 10% of children are immune to pertussis 8.5 years after the final dose of pertussis, which increases the chance of contracting pertussis by 1.3 times each year from the last given dose of pertussis. In 2014, California experienced an epidemic of pertussis that affected over 9,000 individuals.14McGirr A. Fisman D.N. Duration of pertussis immunity after DTaP immunization: a meta-analysis.Pediatrics. 2015; 135: 331-343Crossref PubMed Scopus (120) Google Scholar A study conducted after California’s pertussis epidemic found that, despite high vaccination rates in California adolescents, tetanus, diphtheria, and acellular pertussis only offered 69% protection during the initial year of vaccination, which waned by 35% yearly thereafter, resulting in only 9% of recipients having protection 4 years after vaccination.14McGirr A. Fisman D.N. Duration of pertussis immunity after DTaP immunization: a meta-analysis.Pediatrics. 2015; 135: 331-343Crossref PubMed Scopus (120) Google Scholar In 2018, pertussis cases have been reported nationwide. For example, 32 cases have been localized to Flathead City, MT, with 5 of these cases being reported in 1 day.15Davidson M. Health department reports rise in pertussis activity in Flathead Co. 2018.https://nbcmontana.com/news/local/health-department-reports-rise-in-pertussis-activity-in-flathead-coDate accessed: November 29, 2018Google Scholar Colorado and California have also reported increased pertussis cases for 2018.15Davidson M. Health department reports rise in pertussis activity in Flathead Co. 2018.https://nbcmontana.com/news/local/health-department-reports-rise-in-pertussis-activity-in-flathead-coDate accessed: November 29, 2018Google Scholar Healthy People 2020 has established an overall vaccine goal of 90% for children aged 19 to 35 months, 4 to 6 years, and adolescents. Each age group has target goals set for the various recommended vaccines.16Office of Disease Prevention and Health Promotion 2020 topics & objectives: immunization and infectious diseases.https://www.healthypeople.gov/2020/topics-objectives/topic/immunization-and-infectious-diseases/objectivesDate accessed: November 21, 2018Google Scholar For example, the goals set for the diseases discussed in this article are 90% of children aged 19 to 35 months of age will receive 4 doses of diphtheria, tetanus, and acellular pertussis (DTaP) and 1 dose of MMR.16Office of Disease Prevention and Health Promotion 2020 topics & objectives: immunization and infectious diseases.https://www.healthypeople.gov/2020/topics-objectives/topic/immunization-and-infectious-diseases/objectivesDate accessed: November 21, 2018Google Scholar In 2017, 83.4% of US children were vaccinated with at least 4 doses of DTaP, and 91.1% had received at least 1 dose of MMR.17US Centers for Disease Control and PreventionImmunization: percent of children aged 19-35 months receiving vaccinations. 2017.https://www.cdc.gov/nchs/fastats/immunize.htmDate accessed: November 21, 2018Google Scholar For children in the kindergarten age group, the goal states 95% will receive 4 or more doses of DTaP and 2 doses of MMR.16Office of Disease Prevention and Health Promotion 2020 topics & objectives: immunization and infectious diseases.https://www.healthypeople.gov/2020/topics-objectives/topic/immunization-and-infectious-diseases/objectivesDate accessed: November 21, 2018Google Scholar For the 2017/2018 school year, 95.1% had received 5 doses of DTaP, and 94.3% had received 2 doses of MMR.18US Centers for Disease Control and PreventionVaccination coverage for selected vaccines and exemption rates among children in kindergarten – United States, 2017-18 school year.MMWR Morb Mortal Wkly Rep. 2018; 67: 1115-1122Google Scholar Adolescent goals are set at 80% for 1 dose of tetanus, diphtheria, and acellular pertussis.16Office of Disease Prevention and Health Promotion 2020 topics & objectives: immunization and infectious diseases.https://www.healthypeople.gov/2020/topics-objectives/topic/immunization-and-infectious-diseases/objectivesDate accessed: November 21, 2018Google Scholar In 2017, 88.7% of adolescents had received 1 dose of tetanus, diphtheria, and acellular pertussis.19US Centers for Disease Control and PreventionNational, regional, state, and selected local area vaccination coverage among adolescents aged 13-17 years – United States, 2017.MMWR Morb Mortal Wkly Rep. 2018; 67: 909-917Google Scholar Although vaccine rates are near or at the goals set by Healthy People 2020, VPDs continue to steadily rise, representing a public health crisis. The solution must involve addressing a myriad of parental concerns about vaccine safety that includes purported links to autism, immune system overload, and the perception that VPDs no longer exist. It is crucial that nurse practitioners (NPs) remain current on vaccine research and are able to communicate effectively to all parents to aid in vaccine uptake. Parents who delay or decline vaccines are referred to as vaccine hesitant.20McClure C.C. Cataldi J.R. O’Leary S.T. Vaccine hesitancy: where are we and where are we going.Clin Ther. 2017; 39: 1550-1562Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar Vaccine-hesitant parents may request an altered vaccine schedule, choose to extend intervals between vaccines, or postpone vaccines.20McClure C.C. Cataldi J.R. O’Leary S.T. Vaccine hesitancy: where are we and where are we going.Clin Ther. 2017; 39: 1550-1562Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar Some may refuse vaccines entirely.20McClure C.C. Cataldi J.R. O’Leary S.T. Vaccine hesitancy: where are we and where are we going.Clin Ther. 2017; 39: 1550-1562Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar Not only is this a major contributor to the persistence of VPDs but also puts a strain on the NP who must devise an alternate vaccine schedule and spend additional time educating parents on the benefits of vaccines.20McClure C.C. Cataldi J.R. O’Leary S.T. Vaccine hesitancy: where are we and where are we going.Clin Ther. 2017; 39: 1550-1562Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar The NP must also craft a plan to protect other children in the office that medically cannot be vaccinated and a policy for possible dismissal of the parent who delays or declines vaccines.20McClure C.C. Cataldi J.R. O’Leary S.T. Vaccine hesitancy: where are we and where are we going.Clin Ther. 2017; 39: 1550-1562Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar Because vaccines are given when children are healthy, some parents have a difficult time visualizing the benefits when the risks of vaccination are so widely publicized.20McClure C.C. Cataldi J.R. O’Leary S.T. Vaccine hesitancy: where are we and where are we going.Clin Ther. 2017; 39: 1550-1562Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar The American Academy of Pediatrics strongly advises against dismissing vaccine-hesitant parents because this prevents future revisiting efforts.21Barrows M.A. Coddington J.A. Richards E.A. Parental vaccine hesitancy: clinical implications for pediatric providers.J Pediatr Health Care. 2015; 29: 385-394Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar Many vaccine-hesitant parents reevaluate their vaccine decisions; therefore, the NP should capitalize on every visit to promote parental involvement and vaccine uptake.21Barrows M.A. Coddington J.A. Richards E.A. Parental vaccine hesitancy: clinical implications for pediatric providers.J Pediatr Health Care. 2015; 29: 385-394Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar It is clear that vaccine hesitancy is associated with increased outbreaks of VPDs, hospitalizations, emergency department visits, morbidity, and mortality.20McClure C.C. Cataldi J.R. O’Leary S.T. Vaccine hesitancy: where are we and where are we going.Clin Ther. 2017; 39: 1550-1562Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar Gaps in vaccine rates negatively affect herd immunity. Herd immunity occurs when most of the population is immune to a disease, which helps prevent unvaccinated persons from acquiring the disease and also prevents the spread of disease within the community.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar Delaying or refusing vaccinations compromises herd immunity and increases the risk for disease. There are 18 states that allow exemptions for nonmedical reasons: Arizona, Arkansas, Colorado, Idaho, Louisiana, Maine, Michigan, Minnesota, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Texas, Utah, Vermont, Washington, and Wisconsin.22Sun L.H. Kids in these U.S. hot spots at higher risk because parents opt out of vaccinations. 2018.https://www.washingtonpost.com/news/to-your-health/wp/2018/06/12/kids-in-these-u-s-hotspots-at-higher-risk-because-parents-opt-out-of-vaccinations/?noredirect=on&utm_term=.a30039babd3dDate accessed: December 11, 2018Google Scholar In the 2016/2017 school year, nearly 27% of kindergarteners in Camas County, ID, were unvaccinated.22Sun L.H. Kids in these U.S. hot spots at higher risk because parents opt out of vaccinations. 2018.https://www.washingtonpost.com/news/to-your-health/wp/2018/06/12/kids-in-these-u-s-hotspots-at-higher-risk-because-parents-opt-out-of-vaccinations/?noredirect=on&utm_term=.a30039babd3dDate accessed: December 11, 2018Google Scholar Numerous cities reported that 5% of their kindergarten population were unvaccinated.22Sun L.H. Kids in these U.S. hot spots at higher risk because parents opt out of vaccinations. 2018.https://www.washingtonpost.com/news/to-your-health/wp/2018/06/12/kids-in-these-u-s-hotspots-at-higher-risk-because-parents-opt-out-of-vaccinations/?noredirect=on&utm_term=.a30039babd3dDate accessed: December 11, 2018Google Scholar In response to the increased measles cases in 2014, California banned nonmedical exemptions and now have the highest rate of MMR administration and the lowest reported rates of VPDs.22Sun L.H. Kids in these U.S. hot spots at higher risk because parents opt out of vaccinations. 2018.https://www.washingtonpost.com/news/to-your-health/wp/2018/06/12/kids-in-these-u-s-hotspots-at-higher-risk-because-parents-opt-out-of-vaccinations/?noredirect=on&utm_term=.a30039babd3dDate accessed: December 11, 2018Google Scholar Herd immunity thresholds vary by disease; mumps requires that approximately 80% of the population be immune, whereas measles and pertussis require closer to 95% of the population be immune.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar Strong herd immunity is especially important for infants or those who cannot be vaccinated because of a medical problem.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar These populations rely heavily on herd immunity for protection from illness. Safety concerns surrounding thimerosal, a mercury-based additive used to prevent the growth of bacteria, surfaced in the 1990s.23Offit P.A. Vaccines and autism in primate model.Proc Natl Acad Sci U S A. 2015; 112: 12236-12237Crossref PubMed Scopus (4) Google Scholar Thimerosal was under scrutiny for suspected ill effects on brain development and concerns that linked thimerosal to autism.23Offit P.A. Vaccines and autism in primate model.Proc Natl Acad Sci U S A. 2015; 112: 12236-12237Crossref PubMed Scopus (4) Google Scholar Seven studies performed between 2003 and 2007 concluded that there was no relationship between thimerosal and autism.23Offit P.A. Vaccines and autism in primate model.Proc Natl Acad Sci U S A. 2015; 112: 12236-12237Crossref PubMed Scopus (4) Google Scholar Despite these findings, thimerosal additives were removed from routine childhood vaccines in the summer of 2001.23Offit P.A. Vaccines and autism in primate model.Proc Natl Acad Sci U S A. 2015; 112: 12236-12237Crossref PubMed Scopus (4) Google Scholar A link between the MMR vaccine and autism is the most widely publicized vaccine safety concern. Intense debates started in 1998 when Andrew Wakefield, a British gastroenterologist, published a study in The Lancet journal claiming a direct link between the MMR vaccine and autism.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar The article failed to disclose that Wakefield had received money from lawyers representing parents in antivaccine lawsuits.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar Additionally, Wakefield personally selected the subjects, did not obtain human subjects approval, and did not disclose all of his study’s data.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar In 2010, The Lancet retracted the article, and Wakefield was stripped of his medical license, but the damage to the credibility of vaccines was done.1Porteous G.H. Hanson N.A. Sueda L.A. et al.Resurgence of vaccine-preventable diseases in the United States: Anesthetic and critical care implications.Anesth Analg. 2016; 122: 1450-1473Crossref PubMed Scopus (10) Google Scholar Parents worldwide refused to vaccinate their children, and the resurgence of the measles and the mumps accelerated. It took 12 years