Why do we still see chicken pox?

File May 04, 3 54 00 PM
Dr. Friedman discusses chicken pox on KUSI in San Diego. Click on the photo to see the video.

Once upon a time, chicken pox was a common childhood illness that for many of us was a rite of passage.  While my sisters, my friends and I survived with pox scars to show for it, many kids were not so lucky.  Chicken pox is not always the benign illness that some think it is, which is why we now have a vaccine.  Fortunately, we see very little chicken pox these days.  However, due to vaccine refusal, we are seeing outbreaks of chicken pox just like we did with measles in 2015.

What causes chicken pox?

Chicken pox is caused by Varicella Zoster Virus, or VZV.  Initial infection causes varicella, which is chicken pox.  Many years later, the virus can be reactivated and cause a zoster infection, or shingles. This is because the virus lives on the nerve cells and stays quiet until reactivation.  The virus then travels along the nerve causing shingles infection only in the distribution of that nerve.

What are the symptoms of chicken pox?

Chicken pox starts with 1-2 days of fever, headache and a general feeling of being sick.  This is followed by eruption of the classic rash.  The rash initially starts on the face and the center of the body.  It then spreads outward to the arms and legs.  Early on the sores look like little red bumps, but gradually they evolve into watery blisters that then open and crust, or scab, over. Typically, a patient with chicken pox will have a rash that includes all 3 stages at the same time. The whole infection lasts about 5-7 days.

The infection can spread two ways.  The virus is shed from the sores of an infected person and in the respiratory droplets that an infected person releases during a cough or sneeze.  Anyone who breathes in those droplets, or who touches the droplets and then touches their face, can become infected.  People exposed to the virus may not see symptoms until up to 2-3 weeks after exposure.

What are the complications of chicken pox?

Complications from chicken pox include spread of the virus through the body, as well as complications from a secondary bacterial infection.  Some of these complications include:

  • Pneumonia
  • Encephalitis (swelling in the brain)
  • Skin infection
  • Sepsis (blood stream infection)
  • Dehydration
  • Death

How can chicken pox be prevented?

The best way to prevent chicken pox is vaccination.  A complete series of 2 shots with the vaccine gives over 90% protection from the virus.  Although a few people will still get infected, those who are immunized will have a milder disease course and are unlikely to have any of the complications listed above.  Before the vaccine was licensed, thousands of kids were hospitalized with chicken pox and 100-150 kids died from the disease every year.  The chicken pox vaccine was licensed in 1995 and was initially given as a one shot dose.  While this caused a 90% drop in chicken pox cases, it was found that immunity decreases after the first 2 years. Therefore, a 2 shot series is now recommended.


From the NIH

Back to the original question, why are we seeing chicken pox in an era of vaccination?  Outbreaks occur when vaccination rates are low, which is what happened in San Diego as you can see in the video above.  Not only are unvaccinated kids vulnerable to disease, but they also increase the spread of disease due to a break down in herd immunity. Herd immunity is what is required to keep diseases from spreading through a community.  When more kids are vaccinated, the spread of disease stops.  Therefore, the best things parents can do is get their kids vaccinated.

For more information on vaccines in general, visit my post here and talk to your pediatrician.