The AAP recommended in 2007 to give a second dose of Chickenpox vaccine at 4-5 yrs old.  It is because some kids will end up getting
Chicken pox in spite of the vaccine.  Estimates vary 5-20 %.  But the case is mild with 10-40 spots and no fever or lethargy. 
And studies came out this year showing that the children who had a second vaccine had almost as many cases of Chicken Pox
as did those with only one shot of the vaccine.   Because the cases are so mild, I do not push the second dose of
Varicella (Chicken Pox) Vaccine since we are not sure you are just delaying it until adulthood and the real case
of Chicken Pox is so mild and probably lifetime immunity.  If the parent wants it I will give it but until it is required I
will not be pushing it on my patients. I do recommend the first vaccine at 12-18 months old.

CDC VACCINATION INFORMATION ABOUT VARICELLA (CHICKENPOX)

Varicella (chickenpox) is a common childhood disease which can be serious. It spreads when germs pass from an infected person to the nose or throat of others.

Chickenpox causes a rash, itching, tiredness and fever. It can lead to pneumonia, brain damage or death.

A person who has had chickenpox can develop zoster (shingles) years later. Shingles causes a painful skin rash.

About the Vaccine

Chickenpox vaccine is the best way to protect against chickenpox. About 70-90% of people who get the vaccine are protected from chickenpox.

If vaccinated children do get chickenpox, it is usually very mild. They have fewer spots, lower fever, and recover more quickly.

Vaccinated children who get this milder form of chickenpox can still spread the disease to others who are not protected.

Who Should Get Chickenpox Vaccine?

Children between 12 and 18 months of age: Most children in this age group should have one dose of chickenpox vaccine.

Children between 19 months and their 13th birthday: All children who have not had chickenpox or gotten chickenpox vaccine should be vaccinated before their 13th birthday. Many doctors will give the vaccine at 11 or 12 years of age to children in need. However, vaccine may be given any time between 19 months and 12 years. Your doctor or clinic can tell you whether your child should be vaccinated.

People 13 and older: Some people 13 or older who have not had chickenpox or gotten chickenpox vaccine should get two doses of the vaccine 4 to 8 weeks apart. Ask your doctor for details.

Chickenpox vaccine may be given at the same time as other vaccines.

Most doctors recommend chickenpox vaccine for almost all young children. But there are some cautions. Tell your doctor or nurse if the person getting the vaccine:

• ever had a serious allergic reaction to chickenpox vaccine, neomycin, or gelatin

• now has moderate or severe illness

• is pregnant

• is unable to fight serious infections because of:
  

  • a disease (like HIV/AIDS)
    

  • treatment with drugs such as long-term steroids
    

  • any kind of cancer
    

  • cancer treatment with x-rays or drugs
    

• has gotten blood products (such as immune globulin or a transfusion) during the past several months

If you are not sure, ask your doctor or nurse.

What are the risks from chickenpox vaccine?

As with any medicine, there are very small risks that serious problems, even death, could occur after getting chickenpox vaccine.

However, almost all people who use the vaccine have no problems. It has not been shown to cause any serious problems.

The risks from the vaccine are smaller than the risks from the disease.

Mild Problems

• soreness, redness or swelling where the shot was given (about 1 out of 5 doses)

• very mild rash or several small bumps (3-4 out of 100 doses) [NOTE: It may be possible for someone who gets a rash from chickenpox vaccine to give chickenpox to another person. If the person getting the vaccine is in close contact with anyone whose immune system is not working properly, tell your doctor or nurse.]

• fever of 102° (15 out of 100 doses) [NOTE: Do not use aspirin to reduce fever in children. Ask your doctor or nurse about medicines to control fever.]

Moderate Problems

• a seizure (jerking and staring spell) usually caused by fever (less than 1 out of 1,000 doses). This may not be related to the vaccine.

What to do if there is a serious reaction:

• Call a doctor or get the person to a doctor right away.

• Write down what happened and the date and time it happened.

• Ask your doctor, nurse, or health department to file a Vaccine Adverse Event Report form, or you can call: (800) 822-7967 (toll-free)

If you find that you were pregnant when you got the chickenpox vaccine, or if you get pregnant within 3 months after getting the vaccine, contact your doctor or call this number: (800) 986-8999 (toll-free).

If you want to learn more, ask your doctor or nurse. She/he can give you the vaccine package insert or suggest other sources of information.

Source:

U.S. Department of Health and Human Services
Centers for Disease Control