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Posts Tagged ‘herd immunity threshold’

Why Should Vaccinated Individuals Worry About Measles Outbreaks?

The United States is well on our way to a record year for measles cases.  So far in 2017, we’re on track to see more cases this year than last year.

In the state of Minnesota alone, where a Somali-American community was encouraged to refuse MMR vaccine during visits from Andrew Wakefield and other vaccine critics, a drop in vaccination rates has resulted in a dangerous measles outbreak.  So far, the Minnesota Department of Health has identified 66 total cases spread among four counties, with many cases involving the hospitalization of children.

SOTI-MeaslesCasesIG As the number of measles cases in MN is expected to climb, health departments across the U.S. are beginning to identify other measles cases as well.

For instance, the Maryland Department of Health is investigating a potential outbreak after a patients was admitted to Children’s National Medical Center in the District.  The patient had previously sought medical treatment at Prince George’s Hospital Center in MD, exposing countless people in that area as well.  Meanwhile, a teenaged tourist staying in a NJ hotel contracted measles, and now the New Jersey State Health Department fear other people may have been exposed before the patient was treated at The Valley Hospital in Ridgewood, NJ.

With measles cases emerging across the U.S., and large-scale outbreaks of measles being reported by the World Health Organization in places like Romania and Italy, it’s important to ask if measles outbreaks should be a concern to those who are vaccinated.  

Aren’t vaccinated individuals protected during outbreaks?  And if so, why should we care if others remain unvaccinated?

When it comes to infectious diseases like measles, one person’s decision not to vaccinate can negatively impact the health of others.  There are plenty of unvaccinated individuals who rely on protection from the vaccinated, to include children under one year of age who are too young to be vaccinated for measles, individuals who have medical reasons that restrict them from being vaccinated, or people with compromised immune systems.  These individuals are all at great risk of contracting measles and suffering serious complications and the only protection they have comes from those who are vaccinated.

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In fact, in order to keep measles from spreading, about 92-95% of the population needs to be immune to the disease.  Unfortunately, in the case of measles, even small pockets of un-immunized individuals can threaten the herd immunity threshold.  This is exactly why we are seeing an outbreak in Minnesota.

What’s the big deal?  Is measles even that dangerous? Read more…

College Mumps Cases Here, There and Everywhere

March 18, 2016 40 comments

As a parent of a college student it concerns me to hear of so many reported mumps cases on various college campuses throughout the nation. 

In just the past week, I’ve read about cases at the following colleges:   University of San Diego (5), Harvard University (13), Boston University (3), Tufts University, The University of Massachusetts Boston, Bentley University, University of Southern Maine, Indiana University (12), Butler University (21), IUPUI (3), SUNY Buffalo, University of Kentucky and University of Louisville.  Now there are even reports of new cases in elementary, middle and high schools in Montana and cases expanding in Monroe County just outside of Indiana University.

Mumps112315While there are far fewer cases of mumps these days (1,057 cases in 2015) compared to the years before the vaccine was introduced, I can’t help but wonder what is prompting these recent outbreaks.

Mumps is typically so uncommon that just a few cases in one geographical area can constitute an outbreak.  However, these recent outbreaks seem to be occurring mostly on college campuses, but they are not isolated to one geographic region.

Are we to suspect that the behavior and living conditions among college students is contributing to the transmission of mumps among this particular age group more so than among other age groups?

After all, mumps is a contagious disease that is spread through coughing, sneezing, close contact and saliva exposure with infected people.  One such explanation offered in The Journal of Infectious Diseases suggests that

“High population density in communal living situations, such as dormitories and boarding schools, may provide increased opportunities for close contact or saliva exposures and higher dose exposures to mumps virus when introduced, resulting in easier transmission and higher rates of disease than might occur in other parts of society”.

This seems plausible, but there are likely other factors at play as well.

Could these outbreaks be the result of lower vaccine efficacy, waning immunity or a reduced herd immunity threshold? Read more…