A Cross-sectional Study on Hepatitis B Immune Status Among Vaccinated Healthcare Workers in Khartoum, Sudan

Background: Hepatitis B virus (HBV) infection can lead to chronic hepatitis, liver cirrhosis, and Hepatocellular Carcinoma (HCC). Vaccination against the virus plays an important role in its prevention. Health personnel at risk of infection are recommended to receive the vaccine and to check their immune status thereafter. Objective: To determine Hepatitis B Immune status among vaccinated health personnel in Khartoum state, Sudan. A total of 106 health personnel from different hospitals and doctors’ mess in Khartoum and from different jobs were surveyed and their HBV surface antibodies levels were determined by HBsAb (Quantitative) ELISA Kits. Methods: The those and for more than 50% of those surveyed. About 56.6% (60) of the health personnel involved took three or more doses of HBV vaccine while the rest received one or two doses. The results of the participants who received three or more doses of the vaccine represented immunity by 70%. In general, about 47.2% (50) of the participants in this study did show excellent immune response (>100 mIU/mL) and 18.9% (20) had weak protective levels (between 10 and 100 mIU/mL) So, we concluded that HBV post-vaccination immunity status of health personnel in Khartoum state is lower than post-vaccination HBV immunity in other parts of the world. There is an


Introduction
Hepatitis B Virus (HBV) is a member of the Hepadnaviridae family with a small DNA virus and unusual features of replication similar to retroviruses, in which HBV can replicate through an RNA intermediate and forming a stable minichromosome (cccDNA) in the nucleus. These features of the HBV replication cycle give it the ability to persist in infected cells [1]. HBV can cause acute hepatitis and can also lead to other more serious complications like Chronic Hepatitis, Liver Cirrhosis, and Hepatocellular Carcinoma (HCC) [2]. HBV can survive outside the body for up to seven days; the virus incubation period is around two and a half months. The virus can be transmitted perinatally from a mother to her baby, horizontally by exposure to infected blood or blood products, or through direct spread percutaneously or to mucosal membranes [3]. HBV infects more than 300 million people worldwide; Sudan is classified among the countries with high HBV seroprevalence. Exposure to the virus varied from 47 to 78%, with a hepatitis B surface antigen prevalence ranging from 6.8% in central Sudan to 26% in southern Sudan [4]. HBV vaccine is a recombinant DNA vaccine that contains HBsAg genetically engineered from the yeast Saccharomyces cerevisiae. It provides a seroprotection rate of 85-100% that was seen one month after the last dose of vaccine and it confers immunity for at least 10 years [5]. Hepatitis B vaccine is recommended for unvaccinated adults who are at risk for HBV infection like people whose sex partners have hepatitis B, sexually active persons who are not in a long-term monogamous relationship, persons seeking evaluation or treatment for a sexually transmitted disease, men who have sex with men, people who share needles, syringes, or other drug-injection equipment, household contacts of HBV-infected persons, health personnel and public safety workers at risk for exposure to blood or body fluids, residents and staff of facilities for developmentally disabled persons, persons in correctional facilities, victims of sexual assault or abuse, travelers to regions with increased rates of hepatitis B, people with chronic liver disease, patients on hemodialysis, HIV infection, or diabetes, and anyone who wants to be protected from HBV. The vaccine is usually given as three shots over a period of a six-month period [6]. Serum antibody to the hepatitis B surface antigen (anti-HBs) has long been established as a marker of vaccine-induced protection against hepatitis B. An anti-HBs level of ≥10 IU/ml has been suggested to indicate protection against hepatitis B disease [7]. Old age in adults, male gender, increased body mass index, smoking, and concomitant disease are some of the factors that may decrease the immunologic response to HBV vaccine [8]. This study was conducted to determine hepatitis B immune status among vaccinated health personnel in Khartoum, Sudan.

Materials and Methods
This is a descriptive cross-sectional study conducted at public hospitals of Khartoum including the Ibn Sina Specialized Hospital, the Alshaab Teaching Hospital, and the Academic Hospital from 30th July to 30th September 2017. The study included healthcare providers working in all departments, including trained nurses, medical attendants, and clinicians -both surgical and medical-related specialties and laboratory technicians.
The investigator approached healthcare workers through the hospital administration and the heads of the departments. A self-administered questionnaire that covered age, gender, job description, total doses of vaccine and the date of the last dose plus other data such as duration since the last dose and a history of immunosuppressive treatment and blood transfusion was used to obtain information from the participants.
The questionnaires were collected from the healthcare workers upon completion by appointment with the participant; 5 ml venous blood sample was collected from the cubital vein under complete possible aseptic conditions in EDTA containers, centrifuged at 3000 rounds per min for 10 min to be separated and stored at -20ºC till it was used.
The ELISA procedure was followed according to the manufacturer's instructions.
In brief, 50 μl of the serum were incubated at 37ºC for 60 min in 118-well microplate coated with HBsAg reactive to HBsAb (anti-HBs). Subsequently, the wells were washed (three times) to remove residual serum. 50 μl of anti-HBs conjugated AB was added and incubated at 37ºC for 60 min. The wells were washed (three times) to eliminate unbound conjugate, 50 μl of enzyme-substrate and chromogen were added and incubated at 37ºC for 60 min; 50 μl diluted stop solution (Sulphuric acid) was added and the plate was read at 450 nm as indicated by the manufacturer.

Interpretation of the result
The cut-off value was estimated by calculating the mean (m) absorbance value of negative control x 2.1.
Cut-off = mean of the negative control x 2.1 For the validity of the accomplishment, the following is required: (a) Negative control means: absorbance of individual negative control values must be <0.9 (b) Positive control means: it must be >1.1 (c) Equivocal means: absorbance of individual equivocal values must be between 0.9 and 1.1. All statistical calculations were done using SPSS for Windows, version 24. About 97 (91.5%) participants took the last dose of vaccine within the past 10 years and 12 (11.3%) took their vaccine during childhood.
The number of subjects who completed the all three doses of vaccine or more were 60 (56.6%), those who took two doses were 23 (21.7%), and those with only one dose were 23 (21.7%), see Table 1.  (Figure 1).
About 34 (32%) participants were exposed to needle stick injury during their work but didn't received treatment, 3 (8.8%) had undergone blood transfusion, and 1 had received Hepatitis B Immunoglobulin after accidental needle injury from Hepatitis B-infected patient and her HBsAb result was excellent at 191.0 mIU/mL (Figure 2).

Discussion
HCWs are at a higher risk of blood-borne infections, especially HBV. Vaccination is effective in protecting 90-95% of adults [9]. According to the World Health Organization (WHO) estimate, hepatitis B vaccination coverage among healthcare workers varies from 18% being lowest in Africa to the highest 77% in Australia and New Zealand [10].   In this study, we examined the level of anti-HBsAb in healthcare personnel in three public hospitals in Khartoum state besides Khartoum doctors' mess; the hospitals were the Ibn Sina Specialized Hospital, the Alshaab Teaching Hospital, and the Academic Teaching Hospital. They were chosen mainly because of their easy accessibility. In this study, 60 (56.6%) participants completed all three doses of vaccine, which is higher compared to the lower vaccination rates found in the other two studies conducted in Ethiopia, one in the Gondar University Hospital (28.7%) [11] and the other at the Adama General Hospital and Medical College (25.6%) [12] while nearly similar results as ours was seen in a study conducted in the Makueni County of Kenya (48%) [13]. Another study reveals a higher percentage of full vaccination (72%) in Libya [14].

Conclusion
From this research, we can conclude that HBV post-vaccination immunity status of health personnel in Khartoum state is lower than the post-vaccination HBV immunity in other parts of the world. So, there is an urgent need for a national protocol of HBV vaccination to improve the immunization status of healthcare workers that includes regular checkups of HBV immunity and easy access to a good-quality vaccine.
To get more accurate results of the response to the hepatitis B vaccine among healthcare workers in Sudan, more large-scale studies should be conducted.