The consequences of vaccine hesitancy

 

In 2000, the United States declared that endemic measles was eliminated within its borders.  There were 86 imported cases and very limited indigenous spread.   Fast forward to 2019, where more than 700 measles cases have been identified in 22 states thus far, with large outbreaks in Washington state and New York.  Worldwide, in the first quarter of 2019, measles incidence increased by nearly 300 percent compared with the same period in 2018.  The US outbreaks are a consequence of American travelers becoming infected abroad and transmitting the virus to unvaccinated individuals upon their return to the United States. It turns out that in an un-immunized population, one person with measles can infect 12 to 18 others, making it one of the most contagious diseases known to man with greater than 90% secondary attack rates among susceptible persons. 

HOW CONTAGIOUS IS MEASLES AND WHAT ARE ITS CLINICAL MANIFESTATIONS?

Measles is acquired by inhaling droplets from an infected person’s nose or mouth when they cough, sneeze or talk.  Because these infectious droplets can remain suspended in the air or live on surfaces, the CDC warns that if you are unvaccinated “you can catch measles just by being in a room where a person with measles has been, up to two hours after that person is gone.”  In addition, infected individuals can transmit the virus four days before they even develop a rash and know they have the disease until about four days after rash onset. 

After an incubation period of 10-12 days, people develop what they think is a typical upper respiratory viral infection, characterized by fever, cough, sore throat, nasal congestion, and conjunctivitis (viral prodrome).  Children may also have diarrhea.  But, several days later, a red rash appears on the face and neck and before spreading all over the body for an average of 3-5 days.

Those at high risk for severe illness and complications from measles include infants and children aged <5 years, adults aged >20 years, pregnant women and people with compromised immune systems.  Complications include pneumonia (1:20), encephalitis (1:1000), and residual neurologic damage (up to 25% of cases) including deafness.  The most common causes of death are pneumonia in children and acute encephalitis in adults.  Out of every 1,000 children who become infected, 1-2 will die from respiratory and/or neurologic complications. 

Subacute sclerosing panencephalitis (SSPE) is a very rare (5-10 cases per million reported measles cases) but fatal degenerative disease of the brain that results from persistent measles virus infection in people who otherwise appear to have fully recovered from the illness.  Onset occurs an average of 7 to 10 years after a person has had measles (range 1 month–27 years), and death generally occurs ∼1–3 years after the onset of symptoms which include insidious, progressive deterioration of behavior and cognition, followed by ataxia and myoclonic seizures.                                                                                      

Measles during pregnancy carries a higher risk of premature labor, spontaneous abortion, stillbirths, and low-birth weight infants.

TREATMENT AND POST-EXPOSURE PROPHYLAXIS

There are no antivirals for the treatment of measles, but pregnant women, infants and those with compromised immune systems can receive immune globulin within six days of exposure in an attempt to prevent or modify the clinical course of the disease.

 WHY DID MEASLES MAKE SUCH A RESURGENCE?

There are several reasons for the current situation including lack of uniform access to health care, complacency among parents, and the “anti-vaxxer movement” which spreads misinformation about vaccines.   Much of the misinformation originated with Andrew Wakefield – a British physician who published a controversial and fraudulent paper in The Lancet claiming there was a link between the MMR vaccine, autism and GI disease back in 1998.  Although Wakefield was discredited, the paper later retracted, and many others refuting its findings published, the damage was done.  Many parents were convinced not to vaccinate for fear of their children developing autism.  This has resulted in sub-optimal vaccination rates and loss of “herd immunity” in which a sufficient proportion of a population is immune to an infectious disease (usually through vaccination) so that its spread from person to person is unlikely.  This helps to protect vulnerable individuals such as newborns and the immunocompromised who cannot receive vaccines.  To achieve herd immunity for measles ~95% of the population needs to be vaccinated.  One dose of MMR vaccine is approximately 93% effective at preventing measles; two doses are approximately 97% effective.  

According to UNICEF, the global coverage for the first dose of the vaccine was 85% in 2017, dropping to 67% for the second dose.  National reporting in the US in recent years reveals that ~ 91.5% of eligible children have received ≥1 dose of the vaccine; however, this has not necessarily been uniform across all communities, thus creating the potential for outbreaks. 

How bad will this current measles outbreak be and how long will it last?  No one knows but the stakes are high.  I hope it doesn’t take the deaths or severe injury of our children for us to come to our senses and stop this regressive behavior.

Judith Wolf, MD   Associate Director, WHEP

https://www.cdc.gov/vaccines/pubs/pinkbook/meas.html