More Exemptions and Less Vaccination: The 2 Factors Driving US Measles Outbreaks


Although the majority of states grant vaccine exemptions for medical reasons and religious beliefs, 17 states allow exemption for personal or moral beliefs, increasing the likelihood of outbreaks of preventable diseases like measles.

The recent measles outbreak in New York City is a textbook example of a travel-associated outbreak. Health investigators in the city have determined that the first case was identified in an unvaccinated child who was exposed to measles during travel to Israel.

Legislation in the state of New York permits vaccine exemptions for individuals who have religious beliefs against immunization. As such, cases in this particular outbreak have spread among unvaccinated individuals in Orthodox Jewish communities, but have yet to affect those outside of the religious group, according to the New York City Health Department.

However, New York legislation opposes philosophical exemptions for vaccinations, meaning that children must be up-to-date on required vaccinations in order to attend school unless they have a religious or medical exemption.

The New York City measles outbreak continues to persist, with 67 confirmed cases of measles occurring between October and February 6, 2019.

As travel-associated cases and outbreaks like this one are a cause for concern, it is discomforting to know how much worse this outbreak could have been if New York permitted philosophical exemptions for vaccinations, as 17 other states do, authorizing exemptions for personal, moral, or other beliefs, with circumstances varying state by state.

As measles outbreaks are making headlines across the United States, it’s time to sound the alarm on inappropriate personal vaccine exemptions and confront the deadly consequences of vaccine refusal.

Non-Medical Exemptions and Measles Hotspots

In June 2018, Contagion® reported on a study published in the journal PLOS Medicine, conducted by Peter Hotez, MD, PhD of Baylor College of Medicine’s National School of Tropical Medicine in Houston, Texas, and colleagues.

As part of the study, the investigators identified hotspots around the United States now at risk of measles outbreaks due to a declining rate of measles mumps rubella (MMR) vaccination coverage.

Using the 2015 National Immunization Survey, the investigators determined that there is an inverse association between non-medical exemption rates and MMR vaccine coverage in states that allow the exemptions and identified several metropolitan areas with high exemption rates that could make them vulnerable to measles outbreaks.

The first cities listed as vulnerable? Seattle, Washington; Spokane, Washington; and Portland, Oregon—all 3 of which surround Clark County, Washington, the site of the latest measles outbreak in which 50 cases have been confirmed since January 1, 2019.

Health officials in Multnomah County, Oregon, where Portland is located, have reported 4 cases that are linked to the Washington outbreak, as well.

Washington and Oregon Outbreaks: The Tell-Tale Signs

Both Washington and Oregon permit religious and philosophical vaccine exemptions, according to the National Conference of State Legislatures. Data from the US Centers for Disease Control and Prevention’s 2017 ChildVaxView Report, which details MMR vaccination coverage among children 19-35 months by state and region using data from the National Immunization Survey-Child from 2017, reports that Washington state has the sixth lowest coverage rate in the nation at 88.5%.

The World Health Organization (WHO) reports that in order to reach the measles herd immunity threshold and stop the spread, at least 93-95% of the population must be up-to-date on vaccinations.

According to Clark County’s outbreak investigation statement, all of the confirmed cases are a match of a wild strain of virus that has been circulating through Eastern Europe and is preventable through vaccination.

To date, 48 of the 50 confirmed cases have been identified in children aged between 1 and 18 years. Health records indicate that 43 of the ill individuals were unvaccinated, and vaccination status is unverified in 6 cases. One individual reported receiving 1 dose of the MMR vaccine. Health officials are not providing information about this individual in order to protect their privacy.

“The measles vaccine isn’t perfect, but 1 dose is 93% effective at preventing illness,” Alan Melnick, MD, Clark County health officer and Public Health director, said in the statement. “The recommended 2 doses of the measles vaccine provide even greater protection—97%.”

The Public Health Department also notes that in order to prevent the onset of illness, 1 dose of MMR vaccine must be given to unimmunized people within 72 hours of exposure to the virus. There are currently 3 suspected cases in individuals who received the vaccine more than 72 hours after exposure.

What Other Cities Are at Risk?

According to the aforementioned study, other areas that are considered hotspots include Phoenix, Arizona; Salt Lake City, Utah; Provo, Utah; Fort Worth, Texas; Austin, Texas; Kansas City, Missouri; and Pittsburg, Pennsylvania.

The investigators noted in their report that ending non-medical exemption policies results in increased MMR coverage. Following the 2014-2015 California measles outbreak in Anaheim, which occurred in a population with a measles vaccination rate ranging from 50% to 86, officials passed a measure banning non-medical exemptions statewide.

“State and local health officials now need to work with their state legislatures to close the loopholes that allow non-medical exemptions for reasons of personal belief, as was done previously in California,” said the study’s lead author, Peter Hotez, MD, PhD, in a previous interview with Contagion®.

Dr. Hotez said that the research team is now conducting a follow-up study to investigate the social and political demographics of the urban and rural hotspot areas to help public health officials understand the vaccine hesitancy movement.

Looking Ahead

Where will the next big measles outbreak spring up in the United States?

It could be Harris County, Texas, home of Houston, the city with an estimated 87.8% vaccination coverage, according to the 2017 data, marking the lowest percentage of MMR coverage in a metropolitan area in the United States. Texas, which allows philosophical and religious vaccine exemptions, has 6 confirmed measles cases in 2019, 3 of which have been confirmed in Harris County.

Although we are left to speculate about the next location of a measles outbreak, it’s clear that if vaccination coverage does not increase, it will only be a matter of time until we find out.

For the most recent case counts of measles in the ongoing outbreaks, check out the Contagion® Outbreak Monitor.

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