1. Roxanne E. Williams, MD MPH
Hepatitis B Vaccination Coverage among Students at a US Health Science Graduate School
Roxanne E. Williams, MD MPH
Good Morning,
I’m Roxanne Williams, an Epidemic Intelligence Officer in the Division of Viral Hepatitis at the Centers of Disease Control in Atlanta, GA.
Thank you for the opportunity to discuss our study on hepatitis B Vaccination Coverage among students at a US health science graduate school
Epidemic Intelligence Service Officer
National Immunization Conference
March 30, 2011
National Center for HIV/AIDS, Viral Hepatitis, STD , and TB Prevention
Division of Viral Hepatitis

2. Outline Hepatitis B Virus Infection & Vaccine in Healthcare Workers
Study Rationale & Objectives
Methods
Results
Limitations
Conclusions
In doing so, I will
Provide brief background on Hepatitis B infection and vaccination in HCWs
Discuss our study rationale and objectives
And review study methods, results, limitations, conclusions

3. Hepatitis B Virus in Healthcare Workers
Hepatitis B virus (HBV) is a DNA virus that infects the liver
HBV is transmitted primarily through percutaneous and mucosal exposure to blood
HBV is the most common blood-born pathogen posing occupational risk to healthcare workers(HCW)*
HCW risk is related to degree of contact with blood in workplace
Before introduction of the hepatitis B vaccine, HBV infection prevalence among HCW was ~10 times higher than the general population
Hepatitis B is caused by a DNA virus that infects the liver
It is primarily transmitted primarily through percutaneous and mucosal exposure to blood
Hepatitis B virus (or HBV) is the most common blood-born pathogen that poses an occupational risk to healthcare workers.
- HCWs risk is primarily related to the degree of contact with blood in the work place
-Before introduction of the hepatitis B vaccine, HBV infection prevalence among HCW was ~10 times higher than the general population
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Ciorlia LAS, Zanetta DMT. Hepatitis B in Healthcare Workers: Prevalence, Vaccination and Relation to Occupational Facters. Brazilian Journ of Inf Ds. 2005; 9 (5): *
**Kim, W.R. et.al Hepatology 2009
* J Glob Infect Dis, **CDC, MMWR 2001 & 2006

4. Hepatitis B Vaccine
Hepatitis B vaccine is the most effective means of prevention
Vaccine is well established as a safe and highly effective 3-dose primary series
Hepatitis B vaccination of healthcare workers (HCW) recommended in 1982
Vaccine-induced immunity is assessed by measurement of antibodies against Hepatitis B surface antigen (anti-HBs
A level of anti-HBs ≥ 10 IU/L after completing the primary series is associated with protection
1990s – Postvaccination testing recommended for HCWs
Hepatitis B vaccine is the most effective means of prevention
It is well established AS A safe and highly effective vaccine since its introduction in 1981 and is delivered in a 3 doses primary series.
Because of the high risk of HBV infection among HCWs, CDC and ACIP recommended routine pre-exposure vaccination in 1982.
Vaccine induced immunity is assessed through measurement of antibodies against hepatitis B surface antigen, hereafter referred to as anti-HBs
An Antibody level greater than or equal to 10 international units per liter following the hepatitis B primary vaccination series is associated with protection.
In the 1990s, CDC and ACIP recommended postvaccination testing for HCWs.

5. Study Rationale
Healthcare students are exposed to blood and blood products and thus also at increased risk of exposure to HBV
Little information currently available on Hepatitis B vaccine coverage among healthcare students in the US
There is interest in persistence of protection provided by vaccine since hepatitis B antibody levels decline over time
What are vaccine coverage and antibody levels among healthcare students?
ENTER
Healthcare students are exposed to blood and blood products and thus also at increased risk of exposure to HBV
However, there is little information available regarding hepatitis B vaccination coverage among healthcare students in the US.
Since the vaccine’s introduction, there has been interest in persistence of seroprotection provided by the vaccine since hepatitis B antibody levels decline over time
So,
What is vaccine coverage and antibody levels among healthcare students?

6. Objectives Primary Objectives Secondary Objectives
To determine vaccination coverage and anti-HBs levels among a cohort of US healthcare students
Secondary Objectives
To determine persistence of adequate anti-HBs levels among those who completed the primary series
To evaluate response to booster doses of vaccine
Our primary objective address sought to address this.
Our chief aim was to determine vaccination coverage and antiHBs levels among a cohort of US health care students
ENTER
Our secondary objectives were
- To determine persistence of adequate anti-HBs levels among those who completed the primary series
- and, to evaluate the response to booster doses of vaccine

7. Methods – Design, Setting, Eligibility
Retrospective cohort study in December 2009
Study setting: Midwestern University (MWU)
Private, graduate school in Illinois
Programs in osteopathic medicine, dentistry, and allied health
Eligibility Criteria
Health science MWU students who matriculated from and had a student health clinic record
A retrospective cohort study was conducted in december 2009 at
Midwestern University: a private, graduate school in IL, offering programs in the health sciences including
osteopathic medicine,
dentistry,
and allied health
ENTER
(Physician assistant, physical therapy, occupational therapy, biomedical sciences, clinical psychology, doctor of health sciences)
Eligible participants were
Health science students of Midwestern University who matriculated from
and had a student health clinic vaccination record

8. Methods – Data Collection
Data collected through abstraction of student medical records
Demographic information (date of birth, gender, birthplace, ethnicity)
Dates of Hepatitis B vaccine doses
All postvaccination anti-HBs values with dates
Hepatitis B surface antigen status
Data was collected through abstraction of student medical records to obtain variables of interest (namely):
Demographic information (date of birth, gender, birthplace, ethnicity)
Dates of hepatitis B vaccine doses
All postvaccination anti-HBs values with dates
and Hepatitis B surface antigen status

9. Statistical Methods
Percentage vaccine coverage was compared between students who received ≤3 doses versus 3 doses of vaccine by chi-square test
Association of antibody levels to student characteristics, age at vaccination, time between primary series and postvaccination testing were assessed by t-test and chi-square test
Percentage vaccine coverage was compared among students who received <3 doses and those who received 3 doses of vaccine by chi-square testing
Association of antibody levels to
student characteristics,
age at vaccination, time between primary series and postvaccination testing
were assessed by t-test and chi-square test

10. Study Population & Completeness of Vaccination Records
health science students matriculated &
had health clinic record
Missing critical data (802)
Chronic HBV (6)
Allergy to vaccine (1)
N=2643 (76.6%)
received ≤3 doses & had anti-HBs values
ENTER
Of 3542 who matriculated from , all had health clinic records and thus all were eligible to participate
809 were excluded due to absence of critical data, chronic HBV infection or allergy to vaccination
The remaining 2643 were those who received less than or equal to 3 doses in their primary series and had documented post vaccination anti-HBS values
2481 (or 71% of eligible participants) completed the primary series.
N=2481 (71.9%)
received 3 doses

11. Proportion of students with anti-HBs ≥10 IU/L, by number of vaccine doses
Number of students
Percentage
Post vaccination antiHBs values were compared between students by number of vaccines doses received. These groups are listed along the X axis and precentage of students
along the y axis.
The left most bar represents all 2643 students who received less than or equal to 3 vaccinations ( or 93%), had acceptable antiHBs levels (meaning levels ≥ 10).
The right bar represents the 2481 students who completed the primary series, of these students 94% of students who completed the series had acceptable anti-HBs levels.

12. Characteristics of students with postvaccination serology, by anti-HBs level (N=2643)
Total
N (%)
Anti –HBs
<10 IU/L
N (%)
Anti -HBs
≥10 IU/L
N (%) OR CI
Gender
Female
1698
(64.0)
134
(7.9)
1564
(92.1)
Ref
Male
945
(36.0) 80
(8.5)
865
(91.5)
1.07
Country of birth* US
1614
(85.4)
132
(8.2)
1482
(91.8)
Other
276
(14.6) 28
(10.1)
248
(89.9)
1.3
Median age at start of primary series (years)
14.7
Range (0-49)
16.5
Range
(0-48.8)
15.7
0.10*
The next 3 tables describe characteristics of the students who received less than or equal to 3 doses AND had postvaccination serology
ENTER
Ref = reference group *t-test

13. Characteristics of students with postvaccination serology, by anti-HBs level (N=2643)
Total
N (%)
Anti –HBs
<10 IU/L
N (%)
Anti -HBs
≥10 IU/L
N (%) OR CI
Gender
Female
1698
(64.0)
134
(7.9)
1564
(92.1)
Ref
Male
945
(36.0) 80
(8.5)
865
(91.5)
1.07
Country of birth* US
1614
(85.4)
132
(8.2)
1482
(91.8)
Other
276
(14.6) 28
(10.1)
248
(89.9)
1.3
Median age at start of primary series (years)
14.7
Range (0-49)
16.5
Range
(0-48.8)
15.7
0.10*
1. The majority (or 64%) of students were female.
Among both males and females, ~90% had anti-HBs suggestive of immunity
ENTER
Ref = reference group *t-test

14. Characteristics of students with postvaccination serology, by anti-HBs level (N=2643)
Total
N (%)
Anti –HBs
<10 IU/L
N (%)
Anti -HBs
≥10 IU/L
N (%) OR CI
Gender
Female
1698
(64.0)
134
(7.9)
1564
(92.1)
Ref
Male
945
(36.0) 80
(8.5)
865
(91.5)
1.07
Country of birth* US
1614
(85.4)
132
(8.2)
1482
(91.8)
Other
276
(14.6) 28
(10.1)
248
(89.9)
1.3
Median age at start of primary series (years)
14.7
Range (0-49)
16.5
Range
(0-48.8)
15.7
0.10*
85% of students were US born. Both foreign born and US born students groups, ~ 90% had levels greater than or equal to 10.
ENTER
Ref = reference group *t-test

15. Characteristics of students with postvaccination serology, by anti-HBs level (N=2643)
Total
N (%)
Anti –HBs
<10 IU/L
N (%)
Anti -HBs
≥10 IU/L
N (%) OR CI
Gender
Female
1698
(64.0)
134
(7.9)
1564
(92.1)
Ref
Male
945
(36.0) 80
(8.5)
865
(91.5)
1.07
Country of birth* US
1614
(85.4)
132
(8.2)
1482
(91.8)
Other
276
(14.6) 28
(10.1)
248
(89.9)
1.3
Median age at start of primary series (years)
14.7
Range (0-49)
16.5
Range
(0-48.8)
15.7
0.10*
Median age at the start of the primary series was ~ 15 years of age.
Gender, country of birth, and median age were NOT associated with anti-HBs levels.
Ref = reference group *t-test

16. Characteristics of students with postvaccination serology, by anti-HBs level (N=2643)
Total
N (%)
Anti –HBs <10 IU/L
N (%)
Anti -HBs
≥10 IU/L
N (%) OR CI
Race/Ethnicity
White, Non-Hispanic
1659
(62.8)
128
(7.7)
1531
(92.3)
Ref
Black, Non-Hispanic 31
(1.2) 5
(16.1) 26
(83.9)
2.3
Asian/Pacific Islander
448
(17) 38
(8.5)
410
(91.5)
1.1
Hispanic 48
(1.8) 6
(12.5) 42
(87.5)
1.7
American Indian/
Alaska Native 2
(0.1)
(0)
(100)
und
Other/Unknown
455
(17.2) 37
(8.1)
418
(91.9)
ENTER
Ref = reference group Und = undefined

17. Characteristics of students with postvaccination serology, by anti-HBs level (N=2643)
Total
N (%)
Anti –HBs <10 IU/L
N (%)
Anti -HBs
≥10 IU/L
N (%) OR CI
Race/Ethnicity
White, Non-Hispanic
1659
(62.8)
128
(7.7)
1531
(92.3)
Ref
Black, Non-Hispanic 31
(1.2) 5
(16.1) 26
(83.9)
2.3
Asian/Pacific Islander
448
(17) 38
(8.5)
410
(91.5)
1.1
Hispanic 48
(1.8) 6
(12.5) 42
(87.5)
1.7
American Indian/
Alaska Native 2
(0.1)
(0)
(100)
und
Other/Unknown
455
(17.2) 37
(8.1)
418
(91.9)
Approximate 63% of students were white,
1.2 % black,
17% asian/pacific islander,
2% hispanic and
less than 1 % american indian/alaska native.
Ref = reference group Und = undefined

18. Characteristics of students with postvaccination serology, by anti-HBs level (N=2643)
Total
N (%)
Anti –HBs <10 IU/L
N (%)
Anti -HBs
≥10 IU/L
N (%) OR CI
Race/Ethnicity
White, Non-Hispanic
1659
(62.8)
128
(7.7)
1531
(92.3)
Ref
Black, Non-Hispanic 31
(1.2) 5
(16.1) 26
(83.9)
2.3
Asian/Pacific Islander
448
(17) 38
(8.5)
410
(91.5)
1.1
Hispanic 48
(1.8) 6
(12.5) 42
(87.5)
1.7
American Indian/
Alaska Native 2
(0.1)
(0)
(100)
und
Other/Unknown
455
(17.2) 37
(8.1)
418
(91.9)
A greater proportion of Blacks, Hispanics students had anti-HBs values under 10, though the difference was not statistically significant
Ref = reference group Und = undefined

19. Interval from primary vaccine series to postvaccination testing among students who received 3 doses of vaccine (N=2481)
Interval (Years)
Total
N (%)
Anti -HBs <10IU/L
N (%)
Anti -HBs ≥ 10 IU/L
N (%)
Odds
Ratio
Confidence Interval
< 5
855
(34.5) 32
(3.7)
823
(96.3)
Ref
5-10
931
(37.5) 81
(8.7)
850
(91.3)
2.45
11-15
634
(25.6) 57
(9.0)
577
(91.0)
2.54
≥ 16 61
(2.5) 5
(8.2) 56
(91.8)
2.30
Time interval from end of primary series to date of post vaccination testing was analyzed.
This interval was categorized as shown here, but ranged from 0 to 24 years.
Ref= reference group

20. Interval from primary vaccine series to postvaccination testing among students who received 3 doses of vaccine (N=2481)
Interval (Years)
Total
N (%)
Anti -HBs <10IU/L
N (%)
Anti -HBs ≥ 10 IU/L
N (%)
Odds
Ratio
Confidence Interval
< 5
855
(34.5) 32
(3.7)
823
(96.3)
Ref
5-10
931
(37.5) 81
(8.7)
850
(91.3)
2.45
11-15
634
(25.6) 57
(9.0)
577
(91.0)
2.54
≥ 16 61
(2.5) 5
(8.2) 56
(91.8)
2.30
Most students had post vaccination testing done within 5-10 years of completing their primary series.
Ref= reference group

21. Interval from primary vaccine series to postvaccination testing among students who received 3 doses of vaccine (N=2481)
Interval (Years)
Total
N (%)
Anti -HBs <10IU/L
N (%)
Anti -HBs ≥ 10 IU/L
N (%)
Odds
Ratio
Confidence Interval
< 5
855
(34.5) 32
(3.7)
823
(96.3)
Ref
5-10
931
(37.5) 81
(8.7)
850
(91.3)
2.45
11-15
634
(25.6) 57
(9.0)
577
(91.0)
2.54
≥ 16 61
(2.5) 5
(8.2) 56
(91.8)
2.30
2.5 % had postvaccination testing done 16 years or more after completing primary series.
Ref= reference group

22. Interval from primary vaccine series to postvaccination testing among students who received 3 doses of vaccine (N=2481)
Interval (Years)
Total
N (%)
Anti -HBs <10IU/L
N (%)
Anti -HBs ≥ 10 IU/L
N (%)
Odds
Ratio
Confidence Interval
< 5
855
(34.5) 32
(3.7)
823
(96.3)
Ref
5-10
931
(37.5) 81
(8.7)
850
(91.3)
2.45
11-15
634
(25.6) 57
(9.0)
577
(91.0)
2.54
≥ 16 61
(2.5) 5
(8.2) 56
(91.8)
2.30
Irrespective of time since primary series to postvaccination testing, there were significantly more students with adequate anti-HBS levels.
(((((Of note, percentage of students with anti-HBs less than 10 plateaus at approximately 8.5% , when tested 5 years of more from time of vaccination.))))))
Ref= reference group

23. Students with 3 primary vaccine doses
Number of booster doses administered among students with anti-HBs <10 IU/L
1 booster dose
(N=31)
No booster dose
(N=17)
3 booster doses
(N=81)
2 booster doses
( N=46)
Students with 3 primary vaccine doses
(N=2481)
Anti-HBs 10 IU/L
(N=2306)
Anti-HBs <10 IU/L
(N=175)
As per Midwestern University policy, students who failed to have anti-HBs levels greater than 10 following completion of the primary series were recommended to receive between 1 -3 booster (or additional) doses.
ENTER
Number of boosters given depended on the interpretation of anti-HBs level.
1 booster was given if levels were considered “just below cutoff”,
2 if “indeterminate”,
And 3 if deemed “not immune”
Of 175 such students,
17 did not receive a booster,
31 got a single booster,
46 received 2 booster doses
and 81 received 3 booster doses

24. Response to booster dose(s) among students with anti-HBs <10 IU/L, by number of booster doses administered (N=175)
Number of booster doses
Number of students boosted
Students with available test results
Anti HBs <10 IU/L
N (%)
Anti HBs ≥ 10 IU/L
N (%) 17
(0) 1 31 24
(100) 2 46 3 81 69
(2.9) 67
(97.1)
1-3
158
110
(1.8)
(98.2)
ENTER

25. Response to booster dose(s) among students with anti-HBs <10 IU/L, by number of booster doses administered (N=175)
Number of booster doses
Number of students boosted
Students with available test results
Anti HBs <10 IU/L
N (%)
Anti HBs ≥ 10 IU/L
N (%) 17
(0) 1 31 24
(100) 2 46 3 81 69
(2.9) 67
(97.1)
1-3
158
110
(1.8)
(98.2)
All students who received 1 or 2 booster doses had documented antiHBs levels at or above 10.

26. Response to booster dose(s) among students with anti-HBs <10 IU/L, by number of booster doses administered (N=175)
Number of booster doses
Number of students boosted
Students with available test results
Anti HBs <10 IU/L
N (%)
Anti HBs ≥ 10 IU/L
N (%) 17
(0) 1 31 24
(100) 2 46 3 81 69
(2.9) 67
(97.1)
1-3
158
110
(1.8)
(98.2)
Only ~3% of those who received 3 boosters had inadequate anti-hbs levels.

27. Response to booster dose(s) among students with anti-HBs <10 IU/L, by number of booster doses administered (N=175)
Number of booster doses
Number of students boosted
Students with available test results
Anti HBs <10 IU/L
N (%)
Anti HBs ≥ 10 IU/L
N (%) 17
(0) 1 31 24
(100) 2 46 3 81 69
(2.9) 67
(97.1)
1-3
158
110
(1.8)
(98.2)
And among all students who received booster doses, 98% had an adequate antibody response.

28. Limitations
Cannot exclude possibility of additional doses not documented in student health clinic record
Time points for collection of anti-HBs levels after vaccination were variable
Results may not be generalizable to other students or non-students of similar age
Student health records are intended primarily for documenting compliance
Our study also had several limitations:
1. Cannot exclude possibility of additional doses not documented in the student health clinic record
2. Time points for collection of anti-HBs levels after vaccination were variable
3. Results may not be generalizable to other students or non-students of similar age
4. Student health records are intended primarily for documenting compliance
1. Data available for analysis was limited to the vaccination record provided to the school by the student
-Therefore we could not exclude the possibility of prior hepatitis B vaccinations or additional doses not documented in that record.
2. There was limited demographic and clinical data available for analysis
For example: BMI listed was at matriculation and there was no smoking history
In addition, the Student health records and database are intended primarily for documenting compliance as per the school’s interest or requirements
3. These results may not be generalizable to other healthcare students, or non students of similar age.

29. Conclusions
75% of students completed the 3-dose Hepatitis B vaccine series
94% of students who completed the 3-dose Hepatitis B vaccine series maintained anti-HBs levels ≥10 IU/L
Most completed the primary series during adolescence (age ~ 15 yrs)
IN CONCLUSION,
75% of students completed the 3-dose Hepatitis B vaccine series
94% of students who completed the 3-dose Hepatitis B vaccine series maintained anti-HBs levels ≥10 IU/L
Most completed the primary series during adolescence (age ~ 15 yrs)
“anamnestic response” can only be assesses with a PVT 2-4 weeks after the
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30. Conclusions
Shorter time interval between vaccination and postvaccination testing was associated with anti-HBs >10 IU/L
Almost all (98%) students with available results had post-booster anti-HBs >10 IU/L after revaccination with 1-3 additional doses
Shorter time interval between vaccination and postvaccination testing was associated with anti-HBs >10 IU/L
Almost all (98%) students with available results had post-booster anti-HBs >10 IU/L after revaccination with 1-3 additional doses
“anamnestic response” can only be assesses with a PVT 2-4 weeks after the
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31. Acknowledgements Division of Viral Hepatitis Midwestern University
Justina Groeger, MPH Joseph Towers, MD
Jim Xing , PhD Catherine Fernandez
Philip Spradling, MD
Illinois Department or Public Health
Craig Conover, MD
Kenneth Soyemi, MD
Elizabeth Barajas, MPH
I’d like to that my collaborators at Midwestern University and the Illinois Department of Public Health, as well as my colleagues in the Division of Viral Hepatitis who assists with this study.
THANK YOU!!!
I’m happy to answer any questions
National Center for HIV/AIDS, Viral Hepatitis, STD & TB Prevention
Division of Viral Hepatitis

32. Additional Slides

33. Characteristics of Excluded Students (n=809)
Total
N (%)
Median age (range)
27 (21-67)
Gender
Female
496
(61.3)
Male
299
(36.0)
Country of birth* US
266
(74.5)
Other 91
(24.5)
Characteristic
Total
N (%)
Race/Ethnicity
White, Non-Hispanic
498
(61.6)
Black, Non-Hispanic 25
(3.1)
Asian/PI
143
(17.7)
Hispanic 18
(2.2)
AI/ AN 1
(0.1)
Other/Unknown
124
(15.3)
Demographic characteristics among excluded students were similar for study participants
Median age was 26 for study participants, and 27 for excluded students
Both populations had similar distribution of gender (with predominance of females around 60%),
White composed largest race/ethnic group folled by asians, blacks, hispanics and ai/an
And most were born in the US

34. Characteristics of Chronic Carriers
2 reported born in US (both asian/pi); 4 born in foreign countries (Poland, China, Vietnam, Russia)
Mean age at time of matriculation(range): (23-40)
6/6 had documented lab or physician record supporting diagnosis
*******What is recommendation for these students*****;

35. Study Population N= 3452 Abstracted Records N= 3140 Excluded due to:
Irreconcilable records (2)
Chronic HBV infection (6)
Allergy to Vaccine (1)
Missing DOB/ age at vaccination (235)
N=2896
Missing Anti-HBs result
N=2708
Limit to those who received 3 doses
N=2693
Have titer result and appropriate vaccination dates
N=2481

36. Characteristics of Students who received at least 1 dose of Vaccine and 1st Titer
Characteristic (N=2896)
Gender
Male = 1057 (36.5%)
Median age at start of primary series (range)
14.7 years ( years)
Race/Ethnicity
White, Non-Hispanic
1811 (62.5%)
Black, Non-Hispanic
36 (1.2%)
Asian/Pacific Islander
485 (16.7%)
Hispanic
55 (1.9%)
American Indian/Alaska Native
3 (0.1%)
Other/Unknown
506 (17.8%)
Foreign-born*
316 (15.1%)
BMI (mean ± std)**
23.5 ± 4.1
Hawaiian/Pacific Islander = 7
Add the vaccine dose # back
*N= **N=2095

37. Age at Hepatitis B Primary Vaccine Series Among Students who received ≤ 3 doses (n=2708)
Age in Years
Anti HBs < 10 mIU/mL
N (%)
Anti HBs ≥ 10 mIU/mL
N (%)
χ2 p-value
< 1 2
(25.0) 6
(75.0)
.0007
1-5 7
(15.6) 38
(84.4)
6-10 48
(9.8)
442
(90.2)
11-20
113
(8.1)
1280
(91.9)
21-30 57
(8.4)
620
(91.6)
31-40 12
(16.0) 63
(84.0)
≥ 40 5 15

38. Median Ages and Time Intervals
Study Population (n=2481)
Median age of first dose in years (range)
14.5 (0-49.2) years
Median age at completion of 3rd dose
15.5 ( ) years
Media time between 1st dose and anti-HBs
8.6 ( mos)
Median time between completion of series and titer(range)
2.2 (0-18) years
Median interval between first booster and repeat anti-HBs *
7.9 (0.5-34) mos
Mean time between completion of series and titer was 4.5 years
* N= 158

39. Time interval from primary vaccine series to postvaccintion testing among students who received 3 doses of vaccine, MWU, 2004 – 2009 (n=2481)
Interval (Years)
Anti HBs <10 mIU/mL
N (%)
Anti HBs ≥ 10 mIU/mL
N (%)
χ2 p-value
< 5 32
(3.7)
823
(96.3)
<.0001
≥ 5
143
(8.8)
1483
(91.2)
Time interval from end of primary series to date of PVT testing was analyzed.
Range of interval time is 0 to 24 years.

40. Characteristics of students with ≤ 3 doses & postvaccination serology (n=2643)
Total
N (range)
Anti- HBs <10 IU/L
N (range)
Anti -HBs ≥10 IU/L OR CI
Median age at start of primary series (years)
14.7 (0-49)
16.5(0-48.8)
15.7 (0-49)
0.10*
Age groups at start of primary series in years
N (%)
Anti HBs < 10 mIU/mL
N (%)
Anti HBs ≥ 10 mIU/mL
<1 8
(0.3) 2
(25.0) 6
(75)
Ref
1-5 45
(1.7) 7
(15.6) 38
(84.4)
0.6
6-10
488
(18.5) 48
(9.8)
440
(90.2)
0.3
11-20
1378
(52.1)
109
(7.9)
1269
(92.1)
21-30
637
(24.1) 37
(5.8)
600
(94.2)
0.2
31-40 69
(2.6)
(11.6) 61
(88.4)
0.4
≥ 40 18
(0.7) 3
(16.7) 15
(83.3)
Median age at start of the primary series was ~ 15 years old. There was no association this variable and anti-HBs value
Age was the categorized to further explore the association of antiHBs value across various age groups at start of primary series.
- Only 8 students received vaccination during infancy and most received it between years of age.
- Regardless of age at which student started primary series, the majority maintained anti-HBs levels suggestive of immunity.
- Vaccination at years of age had protective effect on adequate antibody levels compared to those vaccinated at age than 1.
}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}
Age of MWU students in study(as measured by DOB to time of study)
Mean age = 26.3
Median age = 26
Range=
Ref = reference group *t-test

41. Time interval from primary vaccine series to postvaccintion testing among students who received 3 doses of vaccine, MWU, 2004 – 2009 (n=2481)
Interval (Years)
Anti HBs <10 mIU/mL
N (%)
Anti HBs ≥ 10 mIU/mL
N (%)
χ2 p-value
< 5 32
(3.7)
823
(96.3)
<.0001
5-10 81
(8.7)
850
(91.3)
11-15 57
(9.0)
577
(91.0)
≥ 15 5
(8.2) 56
(91.8)
Time interval from end of primary series to date of PVT testing was analyzed.
This interval was categorized as shown here, but ranged from 0 to 24 years. 24% had PVT testing done 15 years or more after completing primary series.
Irrespective of time since primary series to PVT, there were significantly more students with antiHBS levels greater than or equal to 10.
Of note, percentage of students with anti-HBs less than 10 plateaus at approximately 8.5% , when tested 5 years of more from time of vaccination.

42. Midwestern University Hepatitis B Vaccination Policy
Anti-HBs cutoff level are determined by lab at which test was done
MWU will accept any prior anti-HBs levels done (no time limit)
Booster recommendations:
Anti-HBs Result
# of boosters recommended
Not immune 3
Indeterminate 2
Just below lower limit of immunity 1