Varicella (Chickenpox)

Varicella, commonly known as "chickenpox", is a highly contagious viral infection caused by the Varicella-zoster virus.

Image depicts face with red spots

 

How is Varicella spread?

Varicella is spread through sneezing, coughing, and/or direct contact with skin lesions (damage or injury)1.

sneezing

 

Symptoms

The classic symptom of chickenpox is the appearance of an irritable, itchy rash of red spots. These spots are fluid-filled blisters that eventually dry up and turn into scabs. They usually appear on the face, chest, and back before spreading to other regions in the body. 

Image depicts regions of body where rash may appear

 

Symptoms2 that may appear 1-2 days prior to the rash include:

 

fever

Fever

headache

Headache

weak

Weakness/Fatigue

no food

Loss of Appetite

Complications

Though chickenpox is a mild disease, one may experience severe health issues that can lead to death. Those who are at high risk include newborn infants, adolescents, adults, pregnant women, and individuals with a weakened immune system. Common complications include: 

skin infection

Skin infection

Fluid-filled lung

Pneumonia (lung infection)

Brain swelling

Encephalitis (swelling of the brain)

How long do symptoms last?

Varicella is self-limited (resolves spontaneously); any crusted scabs developed from the rash will disappear within 7 to 10 days.

 

After initial exposure, the virus remains in your body and may be reactivated, causing a different disease known as Shingles. Shingles is a contagious infection that is primarily indicated by heightened pain and may be accompanied by an irritable rash similar to chickenpox.

 

The Varicella Vaccine

"Iggy" the Antibody

There are currently two Varicella-containing vaccines licensed for use in the U.S:

  • Varicella Vaccine (Varivax) 
  • Measles-mumps-rubella-varicella, MMRV Vaccine (ProQuad)

Varicella Vaccine Safety

Figure 1.3 Incidence rates of breakthrough varicella per 1000 PY (person-years) from 1995-2008. Overall rate of lesions decreased overtime after implementation of Varicella vaccine in 1995. 

Graph showing incidence rates of breakthrough Varicella

Lesion: an area of abnormal tissue

Breakthrough: Varicella that occurs in vaccinated individuals after 42 days

1000-PY (person-years): for every 1,000 people observed within 1 year, you would expect 1 breakthrough Varicella case

Table 1.4 Mild and severe adverse events provided by the World Health Organization (WHO). This table uses data derived from a literature search on PubMed in 2008 using keywords "vaccine antigen", "safety", and "adverse events"

Varicella Adverse Effects Table

 

Varicella Vaccine Effectiveness

Figure 2.5 In 4 states that have been reporting Varicella cases annually since before the vaccine implementation, incidence (occurrences) declined an average of 97.4% from 1993-1995 to 2013-2014. Decreases can be noticed with recommendation of the 1st-dose and 2nd-dose.

Varicella incidence time graph

 

Herd Immunity: How It Works

Herd Immunity Image

 

 

 

Communities that have very high rates of vaccination further benefit from herd immunity, conferring increased protection to those unable to receive the vaccination.

Varicella Vaccine Schedule6

Table 3. 

Routine Schedule

 

Table 4. 

Catch-up Schedule

  • Recommended for all adolescents and adults without evidence of immunity 
  • For persons with HIV, the minimum interval between the two doses should be 3 months
  • Varivax has no upper age limit

How do I know if I am protected against Varicella?7

Vaccination Records

Documentation of age-appropriate Varicella vaccination serves as the best evidence of immunity

Medical diagnosis

Diagnosis of Varicella disease history by a healthcare professional is also sufficient.

Test tubes

There can be lab tests done to determine whether you’ve been exposed to chickenpox prior but there is no distinction made between whether it was due to natural disease exposure or the vaccine itself.

Babies born before 1980

Birth in the United States before 1980 is also considered evidence of immunity, but should not be considered as such towards health care professionals, pregnant women, and immuno-compromised persons.

Types of Varicella Vaccines

Both contain live, attenuated (weakened) viral strains

needle

Name: Varivax
Manufacturer: Merck
Protections Conferred: Varicella
Minimum Age: 12 months
Vaccine Safety Insert

needle

Name: ProQuad (MMRV)
Manufacturer: Merck
Protections Conferred: Measles, Mumps, Rubella, Varicella
Minimum Age: 12 months to 12 years
Vaccine Safety Insert

Vaccine Side Effects

Side effects8 from the vaccine are more likely to occur after the first dose than after the second, and go away after a few days

rash

Injection Site Rash or Redness 

joint pain

 Joint or Muscle Stiffness

tenderness at injection site

Injection Site Pain or Soreness 

fever

Fever 

 Table 2.9 

table showing vaccine side effects and rates

 

The Bottom Line

As mentioned before, chickenpox is a mild disease that can lead to severe health issues--including the onset of Shingles at a later age or death. The best way to avoid these complications and chickenpox in general is vaccination. 

Sources

1. Chickenpox (Varicella). National Foundation for Infectious Diseases. https://www.nfid.org/infectious-diseases/chickenpox-varicella/. Published January 25, 2020. Accessed April 13, 2020.

2. Chickenpox. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/chickenpox/symptoms-caus…. Published February 27, 2019. Accessed April 13, 2020. 

3. Baxter RR, Ray PN, Tran TR, et al. Long-term Effectiveness of Varicella Vaccine: A 14-Year, Prospective Cohort Study. Pediatrics. 2013;131(5). doi:10.1542/peds.2012-3303.

4. Information Sheet - Observed Rate of Vaccine Reactions: Varicella Zoster Virus Vaccine. https://www.who.int/vaccine_safety/initiative/tools/Varicella_Zoster_Va…. Published June 2012. Accessed April 13, 2020.  

5. Lopez AS, Zhang JS, Marin MS. Epidemiology of Varicella During the 2-Dose Varicella Vaccination Program — United States, 2005–2014. MMWR Morbidity and Mortality Weekly Report. 2016;65(34):902-905. doi:10.15585/mmwr.mm6534a4. 

6. Catch-up Immunization Schedule - Shell. Centers for Disease Control and Prevention. https://www.cdc.gov/vaccines/schedules/hcp/imz/catchup-shell.html#vacci…. Published February 5, 2020. Accessed April 13, 2020.

7. Smith L. ACIP Recommendations for the Prevention of Varicella. American Family Physician. https://www.aafp.org/afp/2007/1101/p1396.html. Published November 1, 2007. Accessed April 13, 2020.

8. Vaccines: Vac-Gen/Side Effects. Centers for Disease Control and Prevention. https://www.cdc.gov/vaccines/vac-gen/side-effects.htm. Published April 2, 2020. Accessed April 13, 2020.

9. Chickenpox (Varicella) Vaccine. Chickenpox (Varicella) Vaccine | Vaccine Knowledge. http://vk.ovg.ox.ac.uk/vk/chickenpox-varicella-vaccine. Published September 9, 2019. Accessed April 13, 2020.