Varicella Outbreak Investigationand

Varicella Vaccine Effectiveness Assessment through Outbreak

Investigation in Schools

Thein Shwe, VPD EpidemiologistJeannie Shifflett, RN, Varicella Surveillance NurseStephen Frame, BS, Varicella Project Coordinator

Objectives• To describe clinical description, diagnosis and

epidemiology of varicella (chicken pox)• To discuss varicella surveillance in West

Virginia• To understand investigation of an outbreak of

varicella• To review West Virginia varicella surveillance

data including varicella outbreaks • To discuss CDC varicella vaccine effectiveness

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Disease Description

• Primary infection – varicella (chickenpox)• A generalized, pruritic (itchy), vesicular (raised

blistery) rash• Mild fever, and• Other systemic symptoms

• Tends to be more severe in adolescents and adults than in younger children

• Breakthrough chickenpox • Mild and occurred in immunized children

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Epidemiology of Varicella• Agent: Varicella zoster virus (member of

herpesvirus family) – highly contagious • Host: humans – the only source of infection• Mode of transmission:

• Contact with the mucosa of the upper respiratory tract or the conjunctiva

• Person to person: direct contact, airborne droplets, or infected respiratory tract secretions, from contact with vesicular zoster lesions

• Transplacental passage of virus from mother to the fetus

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Epidemiology of Varicella cont.

• Incubation period: 14-16 days (range 10-21 days)• Infectious period: 1-2 days before the rash to

crusting of all lesions• Secondary infection (household contacts): 61-100%• Healthcare associated transmission in pediatric

units• Immunity - lifelong• In temperate climates

• Childhood disease• A marked seasonal distribution • Peak incidence - during late winter and early spring

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Disease Burden

• Prevaccine Era in U. S.• ~ 4 million cases of varicella• 10,500-13,000 hospitalizations (range 8,000-

18,000)• 100-150 deaths each year• Mainly children - ~90% before the age of 15

years• 1970s-1980s

• Highest rate – children 5-9 years of age

• 1990s – highest rate – preschool age group

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Specimen collection video

http://www.cdc.gov/vaccines/vpd-vac/varicella/

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Diagnostic Tests for Varicella-Zoster Virus (VZV) Infection

Test Specimen Comments

PCR Vesicular swabs or scrapings, scabs from crusted lesions, biopsy tissue, CSF

Very sensitive method. Specific for VZV, RT (not readily available) distinguish vaccine strain from wild-type, requires special equipment

DFA Vesicle scraping, swab of lesion base (must include cells)

Specific for VZV, more rapid and more specific than culture, less sensitive than PCR

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Varicella Vaccination in the U. S.One –dose Two-dose

Licensure 1995

ACIPRecommendation

1995 2007

Age 12-15 months of age

13 years and older without evidence of immunity should receive 2 doses, 4-8 weeks apart.

First dose – 12-15 months Second dose – 4-6 years of age

13 years and older without evidence of immunity should receive 2 doses, 4-8 weeks apart.

Vaccine coverage 90% (One dose among children 19-35 months of age in U. S.) - 2007

Vaccine Efficacy 97% (12 months-12 yrs.) 99% (13 years and older)

Effectiveness: 70-90% against any varicella disease 95-100% against severe varicella disease 9WVDHHR-BPH-DIDE

Varicella Surveillance in West Virginia

Varicella Surveillance (WV Communicable Disease Rule 64CSR7)

• Weekly aggregate total • Healthcare providers to local health department• LHD to WVDHHR by using ILI and Chickenpox

form

• Varicella outbreak • Immediately reportable from healthcare

provider to LHD

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Varicella Case Definition (2010)http://www.cdc.gov/ncphi/disss/nndss/casedef/varicella_current.htm

• Clinical description• An illness with acute onset of diffuse (generalized) maculo-

papulovesicular rash without other apparent cause.

• Laboratory criteria for diagnosis• Isolation of varicella virus from a clinical specimen, or • Varicella antigen detected by direct fluorescent antibody test, or • Varicella-specific nucleic acid detected by polymerase chain

reaction (PCR), or • Significant rise in serum anti-varicella immunoglobulin G (IgG)

antibody level by any standard serologic assay.

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Varicella Case Definition 2010http://www.cdc.gov/ncphi/disss/nndss/casedef/varicella_current.htm

• Case Classification• Probable: An acute illness with

– Diffuse (generalized) maculopapulovesicular rash, AND – Lack of laboratory confirmation, AND – Lack of epidemiologic linkage to another probable or confirmed case.

• Confirmed: An acute illness with diffuse (generalized) maculopapulovesicular rash, AND – Epidemiologic linkage to another probable or confirmed case, OR – Laboratory confirmation by any of the following:

• Isolation of varicella virus from a clinical specimen, OR • Varicella antigen detected by direct fluorescent antibody test, OR • Varicella-specific nucleic acid detected by polymerase chain reaction

(PCR), OR • Significant rise in serum anti-varicella immunoglobulin G (IgG)

antibody level by any standard serologic assay.

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When you have an Outbreak of Varicella..

12/2009 to 12/2011Notify Varicella Team Immediately

for Assistance at (304)558-5358

Conduct a Preliminary Investigation

• Why? -• To determine if varicella is the likely

cause (verify the diagnosis)• To identify cases and the population at

risk• To determine the magnitude of the

outbreak• To implement control measures

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Verify the Diagnosis

• Know the case definition of varicella

• Know the case definition of varicella outbreak

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Know the Varicella Outbreak Case Definition

(For the purpose of varicella vaccine effectiveness project from 12/09 to

12/11)

• Three (3) cases or more from any facility such as a school or a day care center or a long term care facility, within one incubation period (21 days)

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School “A” Varicella Outbreak

Case 11-1-10

Case 21-24-10

Case 31-31-10

Case 52-25-10

Case 42-5-10

1.Do any of these cases make up an outbreak?2.If so, which of the cases make the outbreak?

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Identify Cases and Contacts..

• Work with the facility’s healthcare personnel and/or administrator

• Collect information• Create a line list

• Name and demographic information• Vaccination information• Clinical information• Laboratory diagnosis if done

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Line listing formhttp://www.wvdhhr.org/idep/pdfs/idep/varicella/Chickenpox_outbreak_line_listi

ng.pdf

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Alert Providers and Notify the Parents…

• Send health alert letter and provider information sheet to HCPs

• Send Parent/Guardian Notification Letter and public information sheet to parents/guardian or general public

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Control the Outbreak

• Isolate(exclude) or cohort:

• Who: all infected persons with varicella or zoster

• How long: until the rash has crusted

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Follow up & Reporting

• Check in with the facility for the status of the outbreak control

• Document and update your regional epidemiologist and DIDE when the outbreak is controlled completely

• Forward completed linelisting form with lab reports if availiable, and other reports to DIDE via Fax: 304-558-8736

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Benefits of Investigating a Varicella Outbreak

• Understand vaccine failure or failure to vaccinate

• Provide estimates of vaccine effectiveness in different outbreak settings

• May identify risk factors for vaccine failure

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Day Care# school(# cases)

Elementary # schools(# cases)

Middle# school(# cases)

High # school(# cases)

Total# school(# cases)

2007 1(34) 6(99) 1(7) 0 8(140)

2008 0 4(51) 4(29) 1(22) 9(102)

2009 0 1(8) 1(10) 0 2(18)

Median #:11(range: 5-40)

2007-2009 Varicella OutbreaksN=19

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Lessons learned from Outbreak Investigation

• Incomplete data

• Low vaccination of varicella among exposed population

• Outbreaks occurred among vaccinated population

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Assessment of Varicella Vaccination Effectiveness through Outbreak

Investigation in Schools

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Background• Varicella outbreaks among school-aged

children – high• 2007 ACIP two dose vaccination

• To reduce the # and size of varicella outbreaks• To assess the impact of routine 2-dose

varicella vaccination• To improve the knowledge about the changing

epidemiology of varicella• To develop and refine appropriate public

health interventions to control and prevent future varicella outbreaks

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Background cont.

• American Recovery and Reinvestment Act (ARRA) funding

• West Virginia – one of 6 sites in the US • Two-year short-term project

• 12/2009 to 12/2011 during school calendar

• Hired 2 staff to assist school nurses: • Jeannie Shifflett: Varicella Surveillance Nurse• Stephen Frame: Varicella Project Coordinator

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Objectives of the Project• To strengthen state and local health

department capacity to detect and investigate varicella outbreaks among school-aged children in a systematic manner

• To strengthen outbreak detection and response in order to evaluate vaccine impact and vaccine effectiveness

• To determine varicella vaccine effectiveness in a school setting to evaluate effectiveness of two-dose varicella vaccination in the context of an outbreak

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Activities for the Project• Varicella vaccine coverage estimates for WV

public schools – SIIS and WV Education Information System (WVEIS)

• Monthly varicella surveillance survey • Varicella outbreak investigation – DIDE

with collaboration of public health nurse, regional epidemiologist to assist school nurses

• Data analysis and reports – epidemiologists

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Varicella Outbreak Investigation in Schools

• Use varicella line list form/case report form– Demographic information– Clinical information

• Onset date, severity

– Vaccination information– Previous disease information – Laboratory testing

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Mild: < 50 lesions, (can easily count)

Moderate: 50-249 lesions, (can place hand on bodywithout covering any lesions)

Moderately severe:250-499 lesions (handplaced on body will cover one or more lesions)

Severe: 500+ lesions (difficult to see normal skin

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• <50 Can count # easily within 30 seconds

• 50 – <250 Patient’s hand can be placed on affected area without covering 1 or more lesions

• 250 – <500 Patient’s hand cannot be placed on affected area without covering 1 or more lesions

• ≥500 Cannot visualize normal skin

Guidance for estimating number of lesions –

proxy for disease severity

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Varicella Vaccine Effectiveness Assessment Study

• Case control study– Recruit well students from the same

classroom/school– Collect data

• Demographic information• Vaccination information• Previous disease information

Follow-up controls to verify if they develop disease 21 days after exposure.

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• Outbreak Toolkit• Monthly Survey Link & Closure Dates• Protocol • FAQ‘s• Additional Information • Emergency and other contact information

School Nurse Resource Web Page

www.wvidep.orgListed Under Hot Topics

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Monthly Varicella Surveillance Survey for School Nurses

How?• School nurse listserve used for contact• Email survey on 30th of every month • Survey deadline – 14th of the following month

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Monthly Varicella Surveillance Survey for School Nurses Cont.

What?• School demographic data• Any varicella case in the school for the month • Any varicella outbreaks in the school for the

month• LHD contact information with outbreak cases

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Sample of Monthly Varicella Survey

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• 13 cases of Varicella reported during the month of December 2009

• No Varicella Outbreaks reported for December• A total of 343 public schools out of the 696 (49%)• A total of 151 school nurses have completed the

survey.• Fourteen(14) Counties reported data for 100% of

their total schools: Boone, Cabell, Clay, Gilmer, Hampshire, Hancock, Lewis, Mercer, Mingo, Ohio, Pleasants, Taylor, Tucker, and Wirt.

December Survey Data

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December Survey Data Cont.Percentages Reported by County

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January Survey Data

• 19 cases of Varicella reported during the month of January 2010

• 1 Varicella Outbreak reported for January• A total of 428 public schools out of the 696 (61%)• A total of 176 school nurses have completed the

survey.• Fifteen(15) Counties reported data for 100% of

their total schools: Boone, Brooke, Gilmer, Hampshire, Hancock, Lincoln, Logan, Mingo, Monroe, Pleasants, Taylor, Tucker, Tyler, Wayne, and Wirt.

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January Survey Data

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Increase In Response

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QUESTIONS ?

THANK YOU