Vaccination Trends

America's vaccination debates rage on, pitting impassioned parents against doctors, educators, and the scientific community. Alarmed by myths both pervasive and pernicious, American families are refusing immunization requirements in disturbing numbers.

These cases are concerning in more ways than one: In addition to rendering individual children vulnerable, vaccination objections imperil the broader public. To contain the spread of contagious illnesses such as measles, only a tiny fraction of the population can be unvaccinated. How do America's vaccination rates compare to ideal immunity standards – and are we hurtling toward an outbreak?

To find out, we studied data from the Centers for Disease Control and Prevention (CDC), analyzing vaccination rates among kindergartners and teenagers. Our results highlight geographical areas in which vaccination rates remain high or show recent improvement – and places that have witnessed a disturbing plunge. Additionally, we researched national vaccination rates for a number of immunizations, presenting trends over time. Ready to see how vaccination controversies are really affecting America's children? Keep reading to find out.

Vaccination Explanations

To contextualize our findings, we've provided a brief overview of several common vaccines and the illnesses they avert. In many cases, these diseases are potentially deadly – and did claim many lives before effective vaccines were developed.

Before the widespread use of the MMR vaccine, for example, millions of Americans would contract measles annually, and hundreds would die as a result. This alarming history sheds light on the consequence of our subject: Immunization must not be taken lightly.

Beside each common vaccine, we've presented a crucial statistic: the vaccination threshold necessary to prevent an outbreak of a given disease. This figure reflects "herd immunity," the concept that immunizing a certain percentage of the population can protect the entire group against illness.

The more contagious a disease, the higher the vaccination threshold to prevent an outbreak. With the highly communicable measles, for example, 90% to 95% of the population must be vaccinated to prevent an outbreak.

Falling Short on Shots?

In recent years, vaccination rates among kindergartners have fluctuated considerably. And while annual changes of 1% or less may not seem dramatic, consider that these tiny deviations represent thousands of kindergartners, each of who is theoretically susceptible to serious illness.

Rates of polio vaccination, for example, dropped more than one percentage point between the school years of 2009–2010 and 2013–2014 before rebounding slightly in subsequent years. This trend could reflect a period of complacency: Given polio's virtual eradication worldwide, parents may not see the vaccine's necessity. Yet, health authorities still assert that this immunization is essential, especially because polio remains a real challenge in other countries.

Similarly, MMR vaccination rates bottomed out between 2011 and 2015 before rising slightly in later years. Throughout this period, however, rates fell short of the 95% threshold sought by experts in public health to prevent possible outbreaks. And because the MMR vaccine is continually dogged by unfounded claims of links to autism, immunization rates may well move further away from that target in the years to come.

Real Progress vs. Regression

In terms of overall vaccination rates, a number of states from various corners of the country have made considerable progress. The most remarkable cases were South Carolina and Iowa, which saw vaccination rates rise almost 9% from 2009 to 2018. South Carolina has been largely spared from measles outbreaks taking shape in other states. Iowa has similarly avoided measles outbreaks for the most part, although 2019 brought the first confirmed cases since 2011. West Virginia and Rhode Island could also claim substantial improvement, with vaccination rates rising roughly 7% during the time frame studied.

In most states, however, overall vaccination rates fell from 2009 to 2018, a sad testament to the surge in so-called "vaccine hesitancy" over the last decade. The decline was most severe in Georgia, where local health officials have been troubled by the spread of anti-vaccine misinformation on social media. Similarly, vaccination rates fell roughly 6% in Arkansas, where the majority of vaccine exemptions are granted on religious or philosophical grounds, rather than for medical reasons. Likewise, in Utah, where vaccination rates fell almost 5%, only a tiny fraction of exemptions are medically justified.

MMR: Rising Resistance

While measles, mumps, and rubella are all highly contagious, measles is especially easy to contract, sometimes lingering in the air for hours. Accordingly, experts have set target thresholds for this vaccination at 95% to avoid potential breakouts – a standard the U.S. failed to meet in any year studied. This challenge is not evident everywhere, however: Many states had exceptionally high vaccination rates, while others fall woefully short.

In Mississippi, for example, less than 1% of kindergartners were unvaccinated. The state does not permit religious or philosophical exemptions to school vaccination requirements and has not reported a case of measles since 1992. West Virginia, which has a similar policy, also boasted enviable MMR vaccination rates.

Yet, even in states that surpass target thresholds, enclaves of vaccine resistance can cause massive problems. In New York, 97% of kindergartners were vaccinated in 2018. In 2019, alarming outbreaks occurred in areas of Brooklyn and Rockland County, where parents had avoided the MMR in large numbers.

Vaccination rates fell below 90% in some states, a critical indicator of measles vulnerability. In Colorado, officials have wrestled with the best approach to encouraging vaccination, with Gov. Jared Polis resisting calls to eliminate nonmedical exemptions. In an attempt to address its dismal immunization rate, Kansas recently imposed new vaccination requirements. Thus far, this move has been met with significant opposition from anti-vaccine groups, which dispute the state's right to mandate any medical procedure.

Polio: Former Threat or Pressing Priority?

As mentioned briefly, polio wrought devastating consequences upon the American public in the years before widespread immunization. So it's particularly troubling to see that polio vaccination rates have fallen significantly as of late, especially in certain corners of the country.

Polio immunization rates mirrored those for the MMR vaccine: Colorado, Kansas, and Idaho had the lowest percentages of immunized kindergartners nationwide. While parents in these places may no longer consider polio a pressing threat, the dangers of anti-vaccine rhetoric are all too evident abroad. In Pakistan, for example, inaccurate propaganda has caused more than a million children to go unprotected – and the disease lives on in that country as a result.

Certain states, however, actually had slightly higher rates of polio vaccination than MMR vaccination. In Delaware and South Carolina, for example, greater percentages of kindergartners were vaccinated against polio than against measles, mumps, and rubella. It's difficult to determine the cause of these disparities, but the differences could reflect relative comfort with the polio vaccine. While the MMR vaccine has been erroneously associated with autism, the polio vaccine has not been similarly singled out by anti-vaccine advocates.

HPV: Tentative Progress

In an undoubtedly hopeful development, the U.S. has recently made significant progress in encouraging adolescents to get vaccinated against human papillomavirus (HPV). Because HPV can eventually lead to cancer and other ailments, public health experts see great promise in rising vaccination rates. Indeed, since the vaccine became widely available, HPV infections and cervical precancers have already plunged.

Overall, female teenagers were more likely than their male counterparts to be vaccinated. Perhaps because most men who contract HPV never experience overt symptoms, parents feel less urgency about getting their male children immunized. Yet, many states had admirable immunization records for male teenagers. In Rhode Island, for example, 4 in 5 teenage boys had been vaccinated (likely because the state's public schools require HPV vaccinations regardless of gender). HPV: Department of Health

Unfortunately, many states had dramatically low rates of HPV vaccination for male and female teenagers alike. Surprisingly, Mississippi belonged to this group, despite a sterling record with other kinds of vaccines. Many experts believe that the HPV vaccine carries a definite stigma for some parents, who balk at the suggestion that their children must be immunized against a virus that is sexually transmitted. Indeed, in states where conservative cultural values predominate, reluctance to discuss sex openly could be a barrier to HPV vaccination.

Immune and Informed: Using Hard Science to Guide Health Decisions

Our results present a mixed view of American immunization, revealing both troubling trends and encouraging developments. For diseases with deadly potential, such as measles and polio, vaccination rates have fallen or remained below ideal thresholds. And despite low immunization rates in some states, American teenagers are getting vaccinated for HPV in unprecedented numbers overall, a development that will surely yield massive public health benefits. Moreover, circumstances differ widely from state to state. Although vaccination remains the subject of national debate, many policy decisions will unfold at the local level.

As families grapple with vaccination fears and questions, one thing is absolutely sure: Their decisions should be guided by valid science, rather than conjecture or misinformation. Accordingly, health information should be affordable and accessible to all. At Health Testing Centers, we make it our mission to help Americans understand their health needs, offering convenient, low-cost medical testing. Get to know our services and find out how we've helped thousands of customers take charge of their own well-being.

Methodology

We analyzed data from the CDC's SchoolVaxView to explore rates of vaccination among kindergartners for the most common and often required vaccines, including MMR, DTaP, polio, hepatitis B, and varicella. We used the CDC's TeenVaxView to analyze HPV vaccination rates among teenagers. The school-level data are reported to the health department by each state.

The aggregate data are reported to the CDC for public and private schools. Data for home-schooled students are not routinely reported to the CDC. CDC SchoolVaxView and related reports don't provide vaccination data of kindergartners for the school year 2010–11.

Vaccination rates were taken from several different sample sizes of youth by the CDC. Target rates are provided by the CDC in "Healthy People 2020."

The types of permitted exemptions vary by state. For specific details, please refer to "School Vaccination Requirements and Exemptions."

Wyoming did not report vaccination data to the CDC in 2018. Washington, D.C., was only included in our analysis of HPV vaccination rates. It is excluded from the other data.

Fair Use Statement

Please help us communicate the importance of immunization to the broader public by bringing this project to your friends, family, and followers. If you do decide to share our work, we ask that you include a link back to this page, allowing others to find and explore all of our results. Additionally, please use our images and information exclusively for noncommercial purposes.