1. National Immunization Conference-April 22, 2010TM
Early Impact of 2-Dose Varicella Vaccination on Disease in West Philadelphia
Rodrerica Pierre1, BA, Dana Perella1, MSPH, Kendra Viner1, PhD, MPH, Niya Spells1, BA, Salini Mohanty1, BS, Adriana Lopez2, MHS, Irini Daskalaki1, MD, E. Claire Newbern1, PhD, MPH, Caroline Johnson1, MD
Introduction
I would also like to take this time to acknowledge my co-authors at PDPH and CDC
1 Varicella Active Surveillance Project, VASP, Philadelphia Department of Public Health, PDPH,
Philadelphia, PA
2 Centers of Disease Control and Prevention, Atlanta, GA
National Immunization Conference-April 22, 2010

2. Impact of 1-Dose Varicella Vaccination on # of Varicella Cases in West Philadelphia.
I will first begin with the Impact of 1-Dose VV on # of Varicella Cases in WP.
In 1995 the varicella vaccine was licensed and a year later (1996) there was a widespread distribution of the vaccine throughout the city of Philadelphia due to the Vaccine for Children Program
In the Fall 2000 varicella vaccine became a school entry requirement for kindergarten students and the following year a school entry requirement for 6th grade students
As result of the vaccine licensure, widespread distribution through out the city, and school entry requirements there has been a significant decrease in the number of varicella cases and an increase in the percentage of children covered by vaccine.
In 2004 coverage rates reached 90% and there was also a 90% decline in cases for month old children,
according to the National Immunization Survey.
S:\DDC\IMM\VASP\Posters and Presentations\surveillance data\VASP9508.ppt
Varicella
Vaccine Licensed
Widespread Distribution of Vaccine in Philadelphia
School Entry
Requirement for Varicella Vaccine in Kindergarten
School Entry
Requirement for Varicella Vaccine in
6th grade
National Immunization Survey, Philadelphia Children months

3. Nationwide Impact of Varicella Vaccination on Disease
Reduction in disease from the 1-dose VV program was similar nationwide.
Outbreaks continued in schools with high varicella vaccination coverage rates (96%-100%).1, 2
Elementary schools
Highest attack rates among younger students
Lasted ~2 months
Index cases were among vaccinated students
1-dose vaccine effectiveness: ~72% - 85%
9-15 cases/outbreak
Even with high 1- dose vaccination coverage, varicella outbreaks (5+ cases) still remain an issue in school settings with high varicella vaccination coverage of (96-100%)
All of these outbreaks had similar patterns. For example:
Most outbreaks occurred in elementary schools,
highest attack rates were among younger students
Each outbreak lasted approximately two months
The index cases were among vaccinated students even though their disease was mild
Vaccine effectiveness was approximately 72-85%
There were approximately 9-15 cases per outbreak
In essence, this data indicates that even in settings where vaccination coverage was nearly universal, the 1-dose vaccination program could not prevent varicella outbreaks completely.
Additional Information
Number of outbreaks in 2005 (b/f 2-dose rec), 15 nationwide that were reported to CDC. This number likely represents only a small fraction of outbreaks that actually occurred. (Reference: Leung et al., JID 2008: 197 (Suppl 2)). Adriana can be contacted for a more recent estimate, but I think the 2005 number of outbreaks works for the presentation since it is the last year before 2-dose implementation.
1.Marin, M. et al. MMWR Recomm Rep 2007: 57 (RR-4):1-40.
2.Civen et al. JID 2008:197 (Suppl 2): S114-S119

4. Impact of 1-Dose Varicella Vaccination on # of Varicella Cases in West Philadelphia.
As a result of the school outbreaks, in 2006 the Advisory Committee on Immunization Practices (ACIP) recommended a second dose of the varicella vaccine for previously vaccinated children 4 years and older
WP incidence graph by year with coverage data:
S:\DDC\IMM\VASP\Posters and Presentations\surveillance data\VASP9508.ppt
Two Doses of Varicella Vaccine Recommended
School Entry
Requirement for Varicella Vaccine in
6th grade
Widespread Distribution of Vaccine in Philadelphia
Varicella
Vaccine Licensed
School Entry
Requirement for Varicella Vaccine in Kindergarten

5. 2 Dose Varicella Recommendation
Dose 1: 12 months to 3 years
Dose 2: >4 years
Routine dose: 4-6 year olds
Catch-up vaccinations:  7 years old
Efficacy: 3-fold decrease in disease compared to single dose
The first dose is usually given any where between 12 months to 3 years old
The second dose is given to children 4yo and older
The routine dose is given at 4-6 yo
Catch up vaccination is given to children 7 years and older
3 fold decrease in disease compared to single dose.

6. OBJECTIVES
To describe adoption of the 2-dose varicella vaccine (VV) in West Philadelphia (WP)
To assess changes in varicella incidence before and after 2-dose VV implementation
To describe adoption of the 2-dose varicella vaccine (VV) in West Philadelphia (WP)
To assess changes in varicella incidence before and after 2-dose VV implementation

7. METHODS - Active Surveillance
Target Area : West Philadelphia
~300,000 residents
300 + community based sites
schools, childcare facilities, hospitals, etc.
Sites report the presence or absence of disease twice a month.
As mentioned before I am with the Varicella Active Surveillance Project (VASP). VASP is a cooperative agreement funded by the CDC and implemented by the Philadelphia Department of Public Health (PDPH) since 1994.
The project’s purpose is to monitor and collect data on (chickenpox and shingles), establish a baseline and to monitor post vaccine epidemiology of varicella
The target area is West Philadelphia: WP represent 1/5 of the city’s and has approximately 300,000 residents. We have over 300 community based sites which include hospitals, schools, child-care facilities, prisons, homeless centers, recreation centers etc.
In order to identify cases each of these sites report the presence or absence of varicella or herpes zoster cases within their facility twice a month. VASP follows up with any sites that do not report for a given time period.

8. METHODS – 2-dose VV Uptake
VV Usage by Healthcare Providers
Healthcare providers (HCPs) participating in VASP reported monthly individual VV doses administered to patients seen by their practice.
2008
VV doses administered by WP HCPs were extracted from the PDPH’s Immunization Registry.
We will first examine the 2- dose varicella vaccine uptake, by looking at how healthcare providers used the varicella vaccine.
In HCP participating in VASP reported individual varicella vaccine doses administered to patients seen in their practice.

9. Vaccine Administration Log
Each month providers would submit this form. They would provide the patients name, DOB, which VZV vaccine was administered and which dose

10. METHODS - 2-dose VV Uptake
VV Usage by Healthcare Providers
HCPs participating in VASP reported monthly individual VV doses administered to patients seen by their practice.
2008
VV doses administered by WP HCPs were extracted from the PDPH’s Immunization Registry.
In 2008 VASP made a shift and began using the Immunization registry to obtain VV information
Before the registry collected immunizations for children 6 years and under.
In July of 2007 the registry expanded to include children through 18 years old.
As a result of the expansion in 2008, VASP was able to use the Immunization Registry for the varicella vaccine administered by WP HCPs

11. IMMUNIZATION REGISTRY
In this image we have a snap shot of a patient’s immunization history. VASP would extract the varicella vaccine data from the patients immunization record.

12. WP kids with ≥ 1 shot in KIDS
METHODS – Vaccine Coverage
2-dose VV Coverage for 2007 and 2008
West Philadelphia children 5-9 years of age
2-dose VV recipients
Dose 1 given on or after 1st birthday (up to 4 days before 1st birthday)
Dose 2 given after July 2006 and 28 days after Dose 1
We used the KIDS Registry to examine vaccine coverage for KIDS in WP
We looked at children 5-9 years old that lived in WP with at least one vaccination that was recorded in KIDS (any vaccination)
Among that group of children, we classified 2 dose recipients
Those who received dose one on or after their 1st b-day
And those who received dose two after July 2006 and 28 days after the first dose
Next, we will examine the 2-dose varicella vaccine coverage for 2007 and 2008
WP 2-dose VV recipients
WP kids with ≥ 1 shot in KIDS
X 100

13. METHODS - Analysis Varicella incidence WP confirmed varicella cases
Pre 2-dose:
Post 2-dose:
Poisson regression:
2007 vs. average incidence (pre 2-dose)
2008 vs. average incidence (pre 2-dose)
Varicella incidence was examined in two time frames
Pre 2-dose:
Post 2-dose:
We then used Poisson regression used to compare
varicella incidence in 2007 to the average incidence in pre 2-dose era
varicella incidence in 2008 to the average incidence in pre 2-dose era

14. Varicella Vaccine Doses Administered to All Age Groups by Year, 2003 to 2008
Number of Doses
2-Dose
Recommendation
(June, 2006)
This graph illustrates the number of varicella vaccine doses administered between 2003 and 2008 in WP
The BLUE= # of Dose 1 YELLOW= # of Dose 2 GREY= # of Unknown Doses
In the pre 2-dose era ( ) there was an average of 5,088 doses administered annually. Following the two dose implementation WP HCP administered 19,044 varicella doses in 2007 and 15,811 in 2008 ( which is 3-4X higher than those administered annually in pre-2-dose era.
: 9%
2nd doses and 34%-47%
Additional Information:
In 2007, most (93%) of the doses administered with unknown dose number were age 5 to 19 years. Most of the gray area on the figure likely represents second doses given to these children, even though we cannot determine this for sure.
WHY??
Since the KIDS registry recently included older children, when VV information was reported for them by their HCP it may have been entered into the registry as their first dose.
Year

15. VV Doses Administered Before and After the 2-Dose Recommendation, by Age Group
Number of Doses
When we look at the varicella vaccine doses administered by age group.
BLUE=1yo ORANGE=5-9yo
We found that there was no change between the pre and post 2 dose era for doses administered to 1 year old. However, there was an increase in the number of doses administered to children in the 5-9 and older.
So this demonstrates the implementation of the 2 dose program if we compare the Pre-2 dose era to the Post 2 dose era
Year
Pre-2nd Dose
Post-2nd Dose

16. 2-dose Varicella Vaccination Coverage
2-dose Varicella Vaccination Coverage Among 5-9 Year Olds by Age,
Age (Years)
2-dose Varicella Vaccination Coverage
2007 %
2008 5 49 61 6 38 62 7 27 52 8 21 42 9 19 36
Overall 30 51
If we focus in on the 5-9 year old age group, the overall coverage was 30% in 2007 and increased to 51% in 2008
Within this age group, we also found that the 5-6 year olds had the highest 2-dose coverage rate of over 60% in 2008

17. Reported Varicella Cases Among All Age Groups by Year, 2003 to 2008
2-Dose
Recommendation
(June, 2006)
Number of Cases
As the years progressed we see a steady decline in the number of cases.
Year

18. Varicella Incidence Among All Age Groups Before and After the 2-Dose Recommendation
28% decline
Cases/100,000 population
Number of Cases
In this graph we see varicella incidence for all ages
We see that there has been a slight decrease in the number of cases in 2007 when we compare it to the pre-2 dose era. And a 28% decrease in if we compare it to the pre 2- dose era which was statistically significant.
Year
(Pre-2nd Dose)
(Post-2nd Dose)
2007: P = .3
2008: P = .01

19. Varicella Incidence Among 5-9 Year Olds Before and After the 2-Dose Recommendation
43% decline
Cases/100,000 population
Number of Cases
If we look at the varicella incidence for the 5-9 year old age group
We see again that there has been a slight decrease in the number of cases in 2007 when we compare it to the pre-2 dose era. And an even greater decrease of 43% in 2008 which was statistically significant.
Year
(Pre-2nd Dose)
(Post-2nd Dose)
2007: P = .97
2008: P = .03

20. SUMMARY
3-4x increase in number of varicella vaccine doses administered in post-2nd dose era
Most additional doses given to children (5+ years)
Coverage rates for children age 5-6 years old reached over 60% in 2008
Varicella incidence declined in the post-2nd dose era
43% decline in incidence among 5-9 year olds
28% decline in incidence among all ages

21. STUDY LIMITATIONS
Vaccine administration data was collected from different sources:
Vaccine Logs vs. KIDS Registry
Completeness of reporting to VASP and Immunization Registry
Vaccine administration data was collected from different sources
Between , data was reported using varicella vaccine administration logs. In 2008, varicella vaccine administration was obtained using Philadelphia’s KIDS Registry.
Completeness has improved in 2007 and 2008.
03-06: 61%
2007: 67%
2008: 71%
Since completeness of reporting is not 100% incidence of disease x could be under-estimated. In completeness of reporting was 61% and increased to 71% in 2008, which suggest that the decrease in disease that we are seeing is not a result a decrease in sites reporting to VASP

22. CONCLUSION
The reduction in varicella incidence that occurred in WP during 2008 may be evidence of the initial impact of the 2-dose VV regimen.

23. QUESTIONS For further information please contact:

24. Extra Slides

25. Proportion of Breakthrough Cases Before and After the 2-Dose Recommendation
Number of Cases
We see that there has been a slight decrease in the number of cases in 2007 when we compare it to the pre-2 dose era. And an even greater decrease in 2008 that was statistically significant.
(Pre-2nd Dose)
(Post-2nd Dose)
Year

26. Varicella Incidence Before and After the 2-Dose Recommendation, by Age Group
Number of Cases
(Pre-2nd Dose)
(Post-2nd Dose)
Year