It’s no secret that I’m an unabashed and staunch supporter of vaccines.  Man’s most influential medical accomplishments: vaccines, antibiotics, and water purification have all contributed to lengthening human life by reducing infectious disease.  The public health implications of vaccination aren’t questioned–epidemiological data clearly show that vaccines work.

However, I continuously find myself defending the personal health implications of vaccines because it’s nearly impossible to know if you ever needed the vaccine in the first place.  Unlike a drug that cures a disease, and thus makes you feel better, we can’t measure the efficacy of vaccination on an individual level.  There is typically no way to know when a vaccine has worked, we only know when it doesn’t or when something bad has happened.

In order for most pathogens to survive, they have to infect a susceptible host. When the majority of people (~90%) are resistant to disease (ie. vaccinated), the pathogen has no where to hide.  It’s important to consider that the 90% threshold doesn’t allow for about 10% of people to refuse vaccines because of personal reasons.  There are many, many children (and adults) who cannot be vaccinated due to actual medical reasons and they depend on the rest of us to make up that 90% and help keep them protected from disease.

Last week, I attended the Clinical Immunology Society (CIS) conference in Boston, MA.  The focus of this conference was primary immunodeficiency disorders (PIDD) and there were many truly heart-wrenching presentations about sick kids with all sorts of infections.  Patients with PIDD are susceptible to pathogens that you or I have with no problems, recurring infections that our natural immunity prevents from happening over and over, and infections that healthy people just don’t normally get sick from.  This is one class of kids for whom some vaccines are dangerous.

The “R” in MMR stands for rubella (also known as German measles), a viral disease that causes congenital anomalies in babies born to infected mothers, much like Zika virus is doing today.  The rubella vaccine was developed in 1969 and added to the combo MMR in 1971.   Since then, the number of cases of congenital rubella syndrome in the U.S. has dropped from more than 60 in 1966 to less than 1 per/year today. The rubella part of the MMR is a weakened version of rubella virus, meaning that it has the potential to cause disease in people with faulty immune systems, including those with PIDDs.

At the CIS conference, Dr. Kate Sullivan from the Children’s Hospital of Philadelphia presented a series of 14 patients with PIDDs who had skin rashes.  A few of these kids had ulcerating, seeping lesions over nearly their entire body.  In the workup of these patients, it became evident that the rashes contained rubella virus, and in 1 patient whose skin biopsy was sequenced, the vaccine strain of rubella was detected.  So, in this patient–and perhaps some of the others, though this is complete conjecture–the rubella vaccine likely caused the skin rashes.

So now that I’ve described a serious adverse event (more commonly known as ‘side effect’) of MMR, it’s important to point out that MMR does not cause rashes in normal, healthy children.  But kids with PIDDs, particularly those with a severe form of the disease missing a white blood cell type called T cells, should not be immunized with MMR or other live-attenuated vaccines.

So, how do we protect kids with PIDDs from rubella infection (or measles and mumps, for that matter)?  Well, it’s actually quite simple: vaccinating everyone around them–especially family and close contacts–creates a barrier of resistance, almost like a wall, preventing rubella virus from reaching them.  This wall is nearly impenetrable, but you can’t know every single person with whom a PIDD patient may come in contact, nor whether they’ve been exposed to a pathogen:  a pre-MMR baby (< 1 year old) at daycare, a kid with a health problem of his own at the playground, or a helpless child on the bus who just happens to have ill-informed parents.

I may be a vaccine advocate, but I am also human, and those images of rubella-stricken PIDD kids from Dr. Sullivan’s presentation won’t leave my mind any time soon.  Vaccines, like everything else that enters your body, are not immune to your body’s natural responses (pun absolutely intended).  Recognizing that parents just want to keep their kids safe, vaccine decisions should not be be made by reading this article or any other website online, but in collaboration with a pediatrician who knows your child’s medical history.  Don’t be afraid to ask questions about vaccines (and anything else the doctor administers or prescribes), but keep in mind the less fortunate kids who cannot get all their vaccines and the difficult medical decisions that their parents have to make on their behalf.

We’re all on this world together, it’s about time we acted like it.

References:
1.  Clinical Immunology Society (CIS).  Immune Deficiency & Dysregulation North American Conference. April 14-17, 2016, Boston, MA.
2.  Vaccines 6th Ed. Plotkin SA, Orenstein WA, Offit PA. Elsevier Inc. 2013.
3.  A look at each vaccine: Measles, Mumps, and Rubella vaccines from the Children’s Hospital of Philadelphia.

For more information on the safety of MMR, check out this video with Dr. Paul Offit.