Before the chickenpox vaccine began to be routinely given in 1995, chickenpox was a very common childhood illness, that even when it wasn't serious, still left children miserable for at least a week. And unfortunately, sometimes these chickenpox infections did become serious, leading to hospitalization and even death.
In the United States, before routine use of the chickenpox vaccine, 'there were an average of 4 million cases of varicella that resulted in 10,500-15,000 hospitalizations and 100-150 deaths every year,'1 many of which occurred in children. Now that Varivax is routinely used, there has been 'a substantial decrease in incidence'2 of chickenpox and its complications.
Although 'varicella vaccination has been found to be highly effective in preventing disease,'3 it is not perfect. Varivax has been shown to be about 71% to 100% effective at preventing chickenpox, with most kids who get a breakthrough infection getting a very mild case of chickenpox. The chickenpox vaccine does offer a greater than 95% protection against moderate and severe chickenpox infections though.
That does leave a lot of kids who still get chickenpox though, including some who get moderate or severe infections, after getting vaccinated with Varivax.
A new recommendation for a chickenpox booster shot from the Advisory Committee on Immunization Practices (ACIP) to the Centers for Disease Control and Prevention (CDC) should help to further decrease chickenpox infections.
The ACIP is now recommending that children get a second dose of the chickenpox vaccine when they are four to six years old. Older children and adults should also get a second dose.
This second dose has been showed to provide increased protection to vaccinated children.
As ACIP recommendations are generally accepted by the CDC, American Academy of Pediatrics, and American Academy of Family Physicians, you can look for this Varivax booster shot to soon become part of the routine childhood and adolescent immunization schedule.
References:1Commentary: the case for universal varicella immunization. Seward JF - Pediatr Infect Dis J - 01-JAN-2006; 25(1): 45-6
2Varicella infections and varicella vaccine in the 21st century. Vazquez M - Pediatr Infect Dis J - 01-SEP-2004; 23(9): 871-2
3Plotkin: Vaccines, 4th ed., Copyright 2004