A data-centric look at vaccines and immunizations in the United States

In 1796, Edward Jenner successfully used cowpox material to immunize individuals against smallpox, creating the earliest variation of the modern vaccine.

Today, the Centers for Disease Control lists 26 diseases against which vaccines provide immunity.

The herd immunity that vaccinations help create, protecting a community by immunizing a critical mass of the population, has helped eradicate or nearly eradicate diseases including diphtheria, pertussis (whooping cough) and polio.

Since 1995, the rate of immunization against diphtheria, pertussis, polio and measles in the United States has increased approximately 5%. Let’s look at the way that increase has unfolded among states and demographic groups.

3-vaccine series

The most basic series of vaccines given to children ages 19-25 months is the 3-series. The 3-series consists of 4 or more injections of the diphtheria, tetanus, and pertussis vaccine (DTaP), 3 or more injections of the polio vaccine, and one or more injections of a measles-containing vaccine (MMR being the most common).

As of 2017, 81.7% of children 19-35 months had received the 3-series. The 3-series immunization rate has generally increased since 1995. However, it has dropped from its peak of 83.5% in 2004.

Immunization by year

Uptake of the 3-series varies a great deal among states. In 2017, Alaska, Missouri, and Wyoming had the lowest uptake while Massachusetts, Virginia, and Maine had the highest uptake. Virginia also had the largest increase in uptake, with 3-series immunization increasing 9% between 2016 and 2017.

Considering annual variation, the average immunization across 2015, 2016 and 2017 reveals different state over and underperformers. The states with the highest average immunization across three years were Massachusetts, New Hampshire and Rhode Island, with Virginia and Maine slipping to fifth and fourth respectively. The states with the lowest average immunization across three years were Alaska, Montana and Wyoming, with Missouri rising to rank above the states with the eight lowest immunization rates.

It is not clear why certain states tend towards low or high immunization rates. The states with high immunization rates tend to have different laws related to vaccination. All states mandate children attending public schools receive vaccinations, but many states allow for religious and philosophical exemptions. However, the states with the highest immunization rates do not have the same laws regarding religious and philosophical exemptions. The same is true of states with low immunization rates.

For example, high immunization states Massachusetts and Virginia both allow for religious exemptions. Furthermore, low immunization states Alaska, Missouri and Wyoming, although they all allow for religious exemptions, do not allow for the more inclusive philosophical exemptions. Therefore, how strict laws regarding vaccination in public schools are does not seem to be the only factor contributing to low or high immunization rates.

Socioeconomic variations

There are also immunization variations among socioeconomic demographics. Those below the poverty line tend to have lower immunization rates than those above or at the poverty line. This gap, however, has narrowed since 1995. In 1995, there was a 9.2% gap in immunization between those below the poverty line and those at or above the poverty line. As of 2017, that gap was 6.1%.

3-series immunization rate by economic status

There also exist variations among racial groups. African American individuals are generally immunized at lower rates than non-Hispanic white individuals.

As of 2017, 84.8% of white individuals received the DTaP vaccine compared to 76.8% of African American individuals. Similarly, 92.5% of white individuals received the polio vaccine compared to 90.3% of African Americans individuals.

The only racial sub-group with higher immunization rates than white individuals is Asian individuals. As of 2017, 86.4% of Asian individuals received DTaP immunization and 94.7% of Asian individuals received polio immunization.

MMR

The Measles, Mumps, and Rubella (MMR) vaccine, which is the most common measles-containing vaccine, is of specific interest because it has consistently been at the center of controversy due to a 1998 study that claimed there was a link between the vaccine and autism. The study has since been debunked by various reports including a 2004 paper published by the CDC.

Although the conclusion of the 1998 study was called into question immediately by members of the scientific and medical communities, it was still able to fuel an anti-vax movement. The paper itself was found to be fraudulent in 2011. The view of the scientific and medical communities is that there is absolutely no link between MMR and autism.

MMR immunization is currently at 91.1% in the United States. This is not much lower than the 91.9% immunization against polio, a vaccine which, by comparison, has faced far less recent controversy.

MMR immunization by year

MMR immunization did fall between 2007 and 2009, when the claims against the MMR vaccine gained additional traction when some celebrities began to endorse the anti-vax movement.

School Exemptions

All 50 states require public school students to have the DTap, MMR, polio, and varicella vaccines or equivalent to attend school. Some private schools have adopted similar requirements. A variety of exemptions, however, are permitted.

Medical exemptions are available in all states. Most states, except for California, West Virginia, New York, Mississippi, and Maine, allow religious exemptions, and sixteen states permit philosophical exemption.

Minnesota, Wyoming, Illinois, Missouri, and Colorado do not report exemption data. However, Alaska, which has the lowest 3-series immunization rate for children 19 to 35 months, has had the highest exemption rate of reporting states since the 2014-2015 school year. In the 2017-2018 school year, 0.8% of children in kindergarten enrolled with an exemption to one or more vaccines.

In the 2017-2018 school year, California had the highest number of exemptions, with 4,190 kindergarten children enrolled with an exemption. The state with the second highest number of exemptions is Florida with 1,051 exemptions. California and Florida are the first and third most populous states respective. Therefore, population is a factor likely contributing to the high number of exemptions in both states. However, the second most populous state, New York, granted only 349 exemptions to children enrolled in kindergarten.

Human Papilloma Virus (HPV)

Introduced in 2006, HPV is among the newer vaccinations. The vaccine was developed partially in response to the rising prevalence of HPV, which is now the most common sexually transmitted disease. It is not required to attend public schools. The CDC recently began to recommend that children receive the vaccine when they are between 11 and 12 years old.

In the past few years, its uptake has been increasing rapidly. The HPV vaccine reached 65.5% adoption among adolescents ages 13 to 17 in 2017. This represented an over 5% increase from its 60.4% adoption rate in 2016. However, its adoption has been somewhat uneven among different states. Wyoming, the state with the lowest uptake, has a 46.9% adoption rate compared to Washington D.C. which has the highest uptake take of 91.1%.

HPV immunization by year

Influenza

The influenza vaccine is also not required to attend public school. Unlike other vaccines, the influenza immunization must be administered annually, whereas most other vaccinations provide immunization for ten years or longer.

The uptake of the influenza shot is much lower, peaking at 47.1% during the 2014-2015 influenza season. As part of the Healthy People program, the Office of Disease Prevention and Health Promotion has a goal of reaching 70% uptake of the influenza vaccine by 2020. However, uptake is currently on a downward trend dipping to 41.7% during the 2017-2018 flu season.

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