News & Views: Test Your Knowledge — Varicella

Varicella disease used to be considered a “rite of passage” during childhood. Yet, since the vaccine has become available, the disease has become less common. So much so that you might not see it regularly or at all in your practice. Check how well you know your facts about chickenpox:

• How is varicella virus transmitted?
• How long is the incubation period (time from exposure to the virus to the appearance of symptoms)?
• What characteristics of the rash can help with the diagnosis?
• Is varicella a reportable condition?
• Who should get vaccinated against varicella and with how many doses?

Varicella transmission

Varicella is transmitted in respiratory droplets (such as from coughs or sneezes) and by direct or aerosolized contact with viral particles from the lesions. Infected individuals are contagious beginning one to two days before the rash starts until the last lesions are crusted.

Incubation period

It takes about two weeks between exposure to the virus and appearance of the first symptoms. In children, rash is often the first noticeable symptom; however, in adults, a one- to two-day prodromal phase, characterized by fever and malaise, may be noticed.

Varicella rashes

Rashes resulting from infection with varicella appear in crops over a period of five to six days. The successive crops advance through similar stages — macules, papules, vesicles, pustules and crusting — but at different times, such that infected individuals can have lesions at different stages on the same body site. The rash tends to concentrate on the trunk and head, but lesions can occur anywhere, including on mucosal surfaces and even the eyes.

Varicella and public health

While varicella is not as contagious as measles, it is among the more contagious of vaccine-preventable diseases. Whereas 10 of 10 susceptible people will become infected with measles, it is typical for 9 of 10 susceptible people to become infected with chickenpox. For this reason, it is important to report varicella diagnoses to your local public health department.

Because reporting by states to the Centers for Disease Control and Prevention (CDC) is not mandatory, CDC data are not representative of all states. However, data reported from 31 states in 2013 indicated more than 11,000 cases of chickenpox.

Varicella vaccination

The first opportunity for vaccination against varicella is at 12 to 15 months of age. A booster dose is recommended between 4 and 6 years of age.

However, infants and young children are not the only people who might need vaccination against varicella. Anyone who does not meet the criteria for immunity to varicella should be immunized with two doses separated by four to eight weeks or one dose if a dose was received previously. People are considered immune if they meet one of the following criteria:

• Written documentation of one or two doses (age-appropriate)
• Blood test indicating immunity
• Disease confirmed by lab testing
• Born in the United States before 1980 — not acceptable for healthcare workers, pregnant women and those who are immune compromised
• History of varicella or shingles disease (diagnosed or verified by a healthcare provider)

Because women infected with varicella during pregnancy can give birth to infants affected by the infection, it is important to ensure that women are immune before becoming pregnant.

Recently, Jessica Leung and colleagues published findings related to the two-dose varicella vaccine recommendations (implemented in 2007) versus the one-dose recommendation (implemented in 1996) in the Pediatric Infectious Disease Journal. The study included data from varicella outbreaks between 2005 and 2012 in six states (CA, MD, MN, TX, VT, WV). Highlights of these findings include:

• A total of 929 outbreaks were reported from the six states during the period reviewed.
• The number of outbreaks per year decreased over the period of study.
• The number of cases involved per outbreak also decreased over time.
• The majority of outbreaks occurred in school settings during the study period; however, the overall percent in schools decreased over time. Increases were seen in other settings, such as daycares, correctional facilities, healthcare facilities, communities and universities.
• The average age of those infected also changed over time. Earlier in the study more than 75 percent of cases were in 5- to 9-year-olds; however, by the end of the study, only about 45 percent of cases were in this age group.

In conclusion, the two-dose regimen is working to decrease the effects of varicella in our communities. However, according to the most recent National Immunization Survey data, U.S. rates for at least one dose of varicella vaccination have lingered around 90 percent since 2010. Therefore, practices should implement procedures to ensure that patients are immune at each opportunity.

References

Adams D, Fullerton K, Jaiosky R, Sharp P. Summary of Notifiable Infectious Diseases and Conditions – United States, 2013. MMWR. Oct. 23, 2015; 62(53); 1-119.

Centers for Disease Control and Prevention. Prevention of Varicella: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR. 2007; 56(RR-4); 1-39.

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases, 13th Ed. Eds. Hamborsky J, Kroger A and Wolfe C. Public Health Foundation, 2015.

Gershon AA, Takahashi M and Seward J. Varicella Vaccines, in Vaccines, 5th edition. Eds. Plotkin SA, Orenstein WA and Offit PA, Elsevier Saunders, 837-69.

Hill HA, Elam-Evans LD, Yankey D, Singleton JA and Kolasa M. National, State, and Selected Local Area Vaccination Coverage Among Children Aged 19-35 Months – United States, 2014. MMWR. August 28, 2015. 64(33); 889-96.

Leung J, Lopez AS, Biostein J, Thayer N et. al. Impact of the US Two-Dose Varicella Vaccination Program on the Epidemiology of Varicella Outbreaks. Pediatr Infect Dis J. 2015; 34(10):1105-9.

Marshall, GS. The Vaccine Handbook: A Practical guide for Clinicians, Fifth Edition. Professional Communications, Inc., 467-77.