Via Research Recognition Day 2024 VCOM-Carolinas

Educational Reports

Analysis of Hepatitis B Titers in Vaccinated Medical Students Chandni Aghera, OMS-III; Nicole Gentile, OMS-III; Haylie Smith, OMS-II; Sena Mazzoleni; Lindsay Tjiattas-Saleski, DO Edward Via College of Osteopathic Medicine – Carolinas Campus, Spartanburg, SC.

Introduction

Results

Conclusions

Table 1 . Association of Categorical Variables with Immunity

Hepatitis B Virus (HBV) is a vaccine preventable liver infection that is transmitted via bodily fluids. This virus can cause transient and chronic infections, ultimately leading to liver failure with cirrhosis and hepatocellular carcinoma. From 1986 to 1989, two noninfectious recombinant DNA vaccines were created, Recombivax HB and Energix-B, and in 1991 the United States implemented a three dose vaccination series recommendation to be completed by 18 months old. 1 This vaccination series can potentially protect against HBV for 30 years . 1 Protection against HBV can be measured using a quantitative titer which measures the level of HBV surface antibodies present within the blood. 2 Previous research classifies a patient as immune if they are found to have a Hepatitis B titer level of greater than 10 mIU/mL after completing a vaccination series at least 1-3 months before. 3 Healthcare workers have an increased risk of infection due to patient exposure; thus, the Center for Disease Control (CDC) recommends that healthcare workers are immunized/tested for HBV. 4 As medical students are entering the healthcare workforce and have ample patient contact during their training, medical schools also have requirements for HBV vaccination and immunity testing prior to or during matriculation. Previous research has shown that subgroups of these students had low titers 5-10 years after completing the vaccination series. 2 Various factors like Body mass index (BMI) over 25, age, smoking, and male sex can contribute to low titers. 5 This study seeks to determine if multiple factors including time between the last dose of the vaccination series and titer measurement, the timing of the dosing, sex of the student, and the age of first dose results in a decrease in Hepatitis B immunity in medical students who have successfully completed the Hepatitis B vaccination series. This cross-sectional study was conducted utilizing data from medical students that have attended the Edward Via College of Osteopathic Medicine- Carolinas Campus from 2015-2023. The inclusion criteria for students were as follows: • Previous or current attendance at VCOM-Carolinas as a medical student • Completion of the Hepatitis B vaccination series immediately before or while attending VCOM • Hepatitis B titers drawn before or while attending VCOM The exclusion criteria were incomplete Hepatitis B vaccination series and inability obtain proper vaccination records. Data was obtained from previously collected vaccination records required upon medical school enrollment. The deidentified data included the subjects’ age, sex, original vaccination dates, vaccine manufacturer, Hepatitis B titer date, repeat vaccination dates and titer dates (if applicable), and final immunity status. The data was then analyzed to identify students who completed the Hepatitis B vaccination series but were found to be non-immune. Data was also analyzed to determine if there is an association between the time of vaccination and titer measurements. Statistical analyses began by calculating descriptive statistics on 2050 subjects. Sample proportions were used to summarize non-immunity and immunity status by year, gender, and total number of vaccine doses received. Sample means and standard deviations were used to summarize central location and dispersion for continuous measures such as age at first vaccination, time since last dose, time between doses, and subject’ age. To test for differences in non-immunity rates by year, gender, and number of vaccine doses, Chi-square analyses were conducted. Due to the skewness observed in the time measures, Wilcoxon Rank Sum Tests were used to compare continuous measures of time between non-immune and immune subjects. To build a regression model predicting non-immunity, logistic regression was used. All analyses were conducted using SAS 9.4. Methods

Key Data: • There is no significant difference in immunity between males and females, which is contradictory to previous literature on the subject. • Time between the initial vaccination series and when the titer is drawn has a negative correlation with immunity; there is an increase in the odds of being non-immune. • Overall, immunity has decreased over the years when comparing the classes of VCOM-Carolinas. Considerations of this study includes the classification of immunity itself. It is generally accepted that a Hepatitis B titer below 10 mIU/L is considered non-immune to HBV. However, some of the previous research has shown that those who had titers below this level still had an immune response when exposed to HBV antigen; it was also found to be unlikely that those who have been vaccinated in the past to get a break through infection even with the lower titer levels. 1 The classification of non-responder is also important to note to compare to low anti-HBV levels. The CDC considers a person to be a non-responder if they still have a titer level below 10 mIU/mL after receiving a second vaccination series; they also recommend testing these individuals for a Hepatitis B infection. 4 With these results, this study shows that those who have a higher risk of contracting HBV may need to be more regularly screened for their Hepatitis B titers and get booster vaccinations as needed. However, boosters are not necessarily warranted for those in the general population due to the lower risk of infection and the likelihood that the initial vaccination is providing immunity at lower levels of Hepatitis B titers.

The results show that there is a significant decrease in the population of students who

are considered immune to Hepatitis B in the classes in increasing order from 2015 to 2027. There also was an insignificant difference in females having a higher rate of immunity comparing to males. There was a significant difference between the percentage of students who were immune after the first two doses compared to those who were found to be non-immune. For those who received three doses of the HBV vaccine, 59.41% of them were immune compared to 40.59% of those who were not.

Table 2 . Means and Standard Deviation of Continuous Variables by Immunity Status

References References

The results show that the age of the first dose in years plays a significant role on immunity. The timing between the doses like the 1st and 2nd, 2nd and 3rd, and 1st and 3rd had no significant difference. The time between the last dose and the immunity test and the age at the immunity test have a significant impact on the data.

Table 3 . Factors that Significantly Predict Non-Immunity in a Logistic Regression Model The logistic regression shows, beginning in the class of 2019 and continuing to the most available class of 2027, a significant rise in the

odds of person being non-immune.As expected, a greater amount of time since immunization is associated with a statistically significant increase in odds of being non immune. For every year since immunization, the odds of being non-immune multiply by 1.07.This change in odds is approximately equal to 0.20 increase in probability of being non-immune if 10 years have passed since immunization for classes of 2019-2027.

Graph 1. Forest Plot of Logistic Regression

The forest plot demonstrates the logistic regression results. The results show that the immunity levels of Hepatitis B have changed over time. Everything listed in the graph is found to be significant.

Edward Via College of Osteopathic Medicine Institutional Review Board, Blacksburg, VA, 2093850-1. Approved: 10/05/23 We would like to acknowledge Dr. David Redden for statistical analysis

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2024 Research Recognition Day