PROTECTING THE HERD: WHY CHARLOTTE SHOULD CARE ABOUT MEASLES
by: Julia Stullken, MPH student, and Dr. Jan Warren-Findlow, MPH Program Director and Associate Professor in the Department of Public Health Sciences
The recent measles outbreaks in Rockland County, New York (2019) and California (2015) are examples of how globalization and insufficient vaccination rates continue to affect the spread of infectious diseases. Measles was considered eliminated in the US in 2000, but due to reduced vaccination rates and increased international travel, the disease made a comeback in the latter years of the decade. This year, the US has seen the highest number of cases since measles re-emerged. The most recently reported outbreaks can be linked to individuals who were exposed to the disease outside of the US, whether due to travel abroad or emigration to the US. Many of the countries where measles was first contracted have lower vaccination rates due to poverty, poor health systems, vaccine shortages, or civil unrest. This makes vaccination prior to travel or upon arrival in the US of the utmost importance.
Measles is a highly contagious viral disease that can be spread through the air and can live outside the body for up to two hours. Infected persons can be contagious for up to four days prior and four days after the onset of the measles rash, which is the most common visual symptom. Other symptoms and complications of measles that make it dangerous include high fever and swelling of the brain. Because of its contagious nature, it is important for all levels of the population – from neighborhoods to states to regions – to maintain what public health officials call “herd immunity.” Herd immunity is the idea that if enough people in a given area are vaccinated, it will protect those who are unable to get the vaccine for medical or religious reasons from acquiring a particular disease. Since measles is so contagious, at least 95% of a given population will need to be immune in order to prevent its spread to unvaccinated individuals and assume herd immunity.
What does Charlotte Have to Do with It?
Fortunately, Mecklenburg County hasn’t reported any cases of measles since December 2014, when a single case was imported (meaning exposure occurred outside of the US). However, there are two characteristics about Mecklenburg County that make immunization compliance extremely important: the social and ethnic diversity of the county, and our position as a travel and business hub. Recent outbreaks in the US have been traced to international tourism, unvaccinated immigrant populations, and unvaccinated US citizens who travel abroad. In all of these instances, the virus was able to spread because of a lack of herd immunity. Having one of the largest airports in the Southeast means we are vulnerable to infection as travelers who have been exposed are passing through or are visiting Charlotte.
One of our strengths in Charlotte is our diverse and culturally rich population. However, our city and county also have neighborhoods with a wide range of socioeconomic statuses and ethnicities. Charlotte is, after all, an immigration hub. An article posted by the Pew Research Center found that Charlotte is one of the most densely populated metropolitan areas when it comes to undocumented immigrants. Approximately 100,000 people living in Charlotte in 2016 were undocumented immigrants. As practitioners and advocates for public health, our role is to ensure that everyone living in Charlotte is protected from infectious diseases and has access to vaccinations. Having accurate numbers on which communities are at risk is important, regardless of socioeconomic status, ethnicity, or documentation status. Vaccination rates are generally counted on a county-wide or state-wide scale, but not by neighborhood subgroups. Even county-wide vaccination rates are limited and not as comprehensive as is needed for proper disease surveillance.
It is difficult to measure the exact degree of vaccine coverage within an individual county due to a variety of factors (medical record keeping, migration, county funding/staffing, etc). In researching this article, we’ve realized how difficult it is to measure the overall immunization rate of a county at any given time. Many counties don’t have a full-time Epidemiologist on staff; even counties who do often experience gaps in reporting from private healthcare organizations or pharmacies who offer vaccines. Since measles is a nationally reportable disease (meaning that confirmed cases must be reported to the state and ultimately the Centers for Disease Control and Prevention (CDC), wouldn’t it make sense for vaccination against measles to be reportable as well? The North Carolina Immunization Registry (NCIR) requests immunizations be reported via an electronic record keeping system, but unfortunately not all providers participate in the registry. We require proof of vaccination for children who attend public schools, but as is the case in many counties, not all children are fully vaccinated within the first 30 days of the school year when data are collected. Not to mention, these measures don’t account for children who aren’t in public school or individuals who come to the US after school-age.
Of the three counties contacted for this article, Cabarrus County is the only one that was able to supply overall vaccination rates across the entire county. According to our source at Cabarrus County, only about 90% of five-year-olds in 2018 had received both recommended doses of the measles vaccine. Recall that to achieve herd immunity, 95% vaccination coverage is required. Gaston County was able to provide data on the number of reported Kindergarteners who had not met the required vaccination schedule in 2017 (approximately 8%); but they indicated that getting an accurate vaccination rate is difficult because of lack of communication between various providers and agencies. The NCIR does not supply county-specific data to the general public.
We were not able to obtain vaccination data from the Mecklenburg County Health Department (MCHD) prior to publishing this article. However, a source at MCHD indicated that the county does not internally measure overall vaccination rates across the county, and instead looks at the rates of vaccination provided in county health clinics. This is worrisome considering the extensive changes made to NCIR over the years to improve vaccination tracking, as well as our position as the largest metropolitan area in North Carolina.
Even though the CDC-reported vaccination rates for the entire state of North Carolina have remained close to herd immunity over the past few years (92% of children younger than three years old in 2017 received at least one dose of the MMR vaccine), an outbreak is not out of the realm of possibility. Not only will those children require a second dose at age five, but the data collected could be missing for the most vulnerable populations (for example, undocumented immigrants). To reach herd immunity we need 95% of the people in any given room, neighborhood, or city to be vaccinated in order to provide protection of those not vaccinated. Measles cases have already been reported in Tennessee this year, and the state has the same immunization rates as NC (92% of children under age three). Border states of South Carolina and Georgia have lower immunization rates (88% and 90%, respectively) which means they have a long way to go before they achieve herd immunity. Since measles has been reported nearby in Tennessee and Georgia, it is important that public health officials and medical providers are prepared for a potential outbreak in NC.
The Mecklenburg County Health Department (MCHD) has several ways of reducing risk and responding to outbreaks of vaccine-preventable diseases. The Communicable Diseases Program has ongoing contact and education efforts with local physicians to help them discuss vaccination with their patients. Alerts generated by the NC Department of Health and Human Services (NCDHHS) are forwarded to providers any time there is an important change in disease risk as defined by the North Carolina Immunization Branch and the CDC. These alerts include information  about where outbreaks are occurring around the country and how many individuals have been affected as well as tips and resources for clinicians. For laboratory confirmed cases of measles, MCHD launches a complete investigation, including potential recent contacts with the patient, and measures to prevent further spread. MCHD follows the CDC’s recommended course of action for preventing the spread of communicable diseases, including immunization, isolation, exclusion and quarantine of patients believed to have measles. Additionally, MCHD’s strategic business plan includes programs and efforts to increase immunization rates, especially among school children.
What should you do about measles?
The best thing to do is educate yourself and your family about vaccination and make sure you are up-to-date with your vaccines. If you are skeptical about vaccination, talk to your primary care provider about the benefits and risks of immunization. Based on what we’ve learned from prior outbreaks, it is important to be vaccinated if you plan to spend time in schools, densely populated areas, or in areas frequented by travelers, such as amusement parks or airports. If you live with someone who cannot be vaccinated for medical reasons, you should be vaccinated to help prevent them from exposure. For more information about Mecklenburg county immunization clinics or where to find your immunization records, visit the Mecklenburg County Health Department website.
Public health officials and clinicians should ensure culturally competent information is available for diverse individuals within our community. This means providing information in different languages and working with community-based organizations to ensure that all areas of the county have adequate access to vaccination. Since measles vaccination requires two doses (the first by age two and the second at age five), strategic follow-up and education is necessary to keep parents and children from falling through the cracks. Preventing an outbreak like the one in New York will require efforts not only from health officials. Collaboration between travel agencies, large companies with many employees, schools, and community leaders is imperative to ensure the prevention and containment of measles.
Additionally, better data collection and stewardship is needed for us to understand the potential risk of an outbreak occurring, as well as helping health departments understand where to focus their resources. Clinicians and local agencies should take steps to participate in the NCIR and share data and resources with other agencies. The more complete our reporting, the better our predictions and recommendations will be.
Acknowledgments and Sources:
Dr. Shi Chen, Assistant Professor at UNC Charlotte
Susan Long-Marin of Mecklenburg County Health Department
Dana Rynk of Cabarrus Health Alliance
Leslie Sellers of Gaston County Department of Health and Human Services
Kita Chandler of the North Carolina Immunization Registry