New study concludes that vaccine refusal helped fuel Disneyland measles outbreak

March 19, 2015
Area(s) of Interest: Public Health Vaccination 

A new study conducted by research teams from MIT and Boston Children’s Hospital has concluded that parental resistance to vaccinations played a role in the Disneyland measles outbreak that started in January.

The analysis, published in JAMA Pediatrics, showed that the highly contagious disease has spread to seven states and two other countries, largely because parents did not vaccinate their children.


The study’s authors used simple math to determine that the vaccination rate among people who were exposed to measles during the outbreak was no higher than 86 percent, and might have been as low as 50 percent. At least 96-99 percent of the population must be vaccinated to establish herd immunity.


The study underscores the need for childhood vaccinations to prevent more outbreaks. Vaccination rates with the measles, mumps and rubella (MMR) vaccine in many of the communities that have been affected by the measles outbreak fall well below the necessary threshold to sustain herd immunity, thus placing the greater population at risk in addition to the unvaccinated, the researchers concluded.


Measles is a highly infectious viral disease that remains a leading cause of death in children worldwide. After patients cough or sneeze, the virus particles can survive as long as two hours on doorknobs, hand rails, elevator buttons and even in the air.


According to the World Health Organization, about 400 people died from measles every day in 2013. However, before vaccination became widespread, the disease killed about 2.6 million people per year.


The study authors said that the index patient in the Disneyland outbreak was probably exposed to measles overseas and then visited the Anaheim amusement park while contagious, according to the Centers for Disease Control and Prevention. This particular strain of measles is identical to one that spread through the Philippines last year, where it sickened about 58,000 people and killed 110.


No deaths have been traced to the Disneyland outbreak.


According to the authors of the study, the extent of the Disneyland outbreak is a reflection of the anti-vaccination movement, which continues to grow despite overwhelming medical evidence that the MMR vaccine does not cause autism or other developmental problems. In most cases, side effects are limited to pain at the injection site, fever, a mild rash or temporary swelling. In rare cases, children may have a severe allergic reaction to the vaccine or develop febrile seizures, joint pain, temporary arthritis or a blood disorder called immune thrombocytopenic purpura.


To see the study, click here.


SB 277 (Pan) is currently moving through the legislature and would remove the option for a personal belief exemption for immunizations, unless medically necessary. The California Medical Association supports the bill, which was recently endorsed by the Sacramento Bee.



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