Varicella (Chicken pox) Class note

Question 1

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What is another name for varicella zoster virus?

Answer 1

Chickenpox

Question 2

How is Varicella transmitted?

Answer 2

Touching or inhalation.

Question 3

How long is Chicken pox contagious for?

Answer 3

1 to 2 days before the rash appears until all the blisters have formed scabs, generally 5 to 7 days after they appear.

Question 4

What is the incubation period of chicken pox?

Answer 4

10 to 21 days from exposure

Question 5

What is the clinical presentation of chicken pox?

Answer 5

• itchy rash that develops into fluid-filled blisters with or without fever
• the blisters rupture and scab
• Rash first appears on the head and trunk and spreads to the extremities
• Usually self limiting but may lead to system complications in infants or immunocompromised individuals.

Question 6

What are serious complications of chicken pox?

Answer 6

• Prolonged fever
• greater number of lesions
• prolonged formation of lesions or pneumonia

Question 7

When is antiviral treatment considered for chicken pox?

Answer 7

Antiviral treatment may be indicated in patients with higher risk of complications, start within 24 hours of rash onset. Immunocompromised individuals will require treatment even if rash began more than 24 hours ago.

Question 8

What are the antiviral medications used for Chicken pox and the doses?

Answer 8

Question 9

What is the estimated efficacy of varicella vaccine?

Answer 9

Efficacy of varicella vaccines in children is estimated to be 94.4% after a single dose and 98.3% after a second dose

Question 10

What are the recommendations regarding vaccinating pregnant women with varicella vaccine, or those who want to become pregnant?

Answer 10

AVOID the varicella virus vaccine in pregnancy.​ Women should delay pregnancy by at least 4 weeks following vaccination with a univalent varicella vaccine.

Question 11

When should systemic antiviral therapy be avoided after vaccination with varicella vaccine?

Answer 11

Systemic antiviral therapy (such as acyclovir, valacyclovir, famciclovir) should be avoided in the peri-immunization period, as it may reduce the efficacy of varicella-containing vaccine.

Chronic anti-viral therapy should be STOPPED at least 24 hours before administration of varicella-containing vaccine and should not be restarted until 14 days after vaccine administration

Question 12

HOw long should salicylates be avoided after administration of varicella vaccine?

Answer 12

Manufacturers of varicella-containing vaccines recommend avoidance of salicylate therapy (medications derived from salicylic acid, such as ASA) for 6 weeks after varicella immunization because of an association between wild-type varicella, salicylate therapy and Reye’s syndrome. However, adverse events have not been reported with the use of salicylates after varicella immunization, hence adults with conditions requiring chronic salicylate therapy should be considered for immunization, with close subsequent monitoring.

Question 13

What is the dosing for the monovalent varicella vaccines in kids 12 months to <13 years?

Answer 13

1st dose: children aged 12-15 months

2nd dose: 18 months or any time thereafter, but no later than around school entry

Recommended interval for 2 doses is 3 months

Question 14

What is the dosing for those 13 years a dn older for monovalent varicella vaccine?

Answer 14

2 doses (recommended interval of 6 weeks, minimum 4 weeks)

Question 15

What is the dosing for MMRV vaccines?

Answer 15

12 months to <13 years old:

1st dose: children aged 12-15 months

2nd dose: 18 months or any time thereafter, but no later than around school entry

Recommended interval for 2 doses is 3 months

Question 16

When should univalent varicella vaccine be given for post exposure management for susceptible healthy non-pregnant persons?

Answer 16

For optimal effectiveness, univalent varicella vaccine should be given as soon as possible, preferably within 72 hours, after exposure. When given up to 5 days after exposure, it has been shown to be approximately 90% effective in preventing or reducing the severity of varicella. Individuals under 50 years of age who have received only 1 dose of varicella-containing vaccine should be offered a second dose.

Question 17

What criteria must be met before an individual gets varicella zoster immunoglobulin?

Answer 17

1. The exposed **person is susceptible **to varicella.
2. There has been a significant exposure to a person with varicella or HZ.
3. The exposed person is at **increased risk of severe varicella. **
4. Post-exposure immunization with univalent varicella vaccine is contraindicated (such as immunocompromised individuals or pregnant women).

Question 18

When should VARIg be administered?

Answer 18

VarIg should be administered as soon as possible following exposure, and ideally within 96 hours after first exposure, after which its benefit is uncertain. HOWEVER, if more than 96 hours but less than 10 days have elapsed since the last exposure, VarIg may still be administered to individuals for whom it is indicated; in this case its primary purpose may be attenuation rather than prevention of disease. Antibodies to varicella zoster (VCZ IgG) should be tested prior to administration EXCEPT in case of hematopoietic stem cell transplant patient.

Question 19

In what situation do we NOT test Antibodies to VCZ IgG before administration of VarIg?

Answer 19

Antibodies to varicella zoster (VCZ IgG) should be tested prior to administration EXCEPT in case of hematopoietic stem cell transplant patient.