Post-vaccination anti-HBs testing among healthcare workers: More economical than post-exposure management for Hepatitis B

Objective: to compare the direct cost, from the perspective of the Unified Health System, of assessing the post-vaccination serological status with post-exposure management for hepatitis B among health care workers exposed to biological material. Method: cross-sectional study and cost-related, based on accident data recorded in the System of Information on Disease Notification between 2006 and 2016, where three post-exposure and one pre-exposure management scenarios were evaluated: A) accidents among vaccinated workers with positive and negative serological status tests for hepatitis B, exposed to known and unknown source-person; B) handling unvaccinated workers exposed to a known and unknown source-person; C) managing vaccinated workers and unknown serological status for hepatitis B and D) cost of the pre-exposure post-vaccination test. Accidents were assessed and the direct cost was calculated using the decision tree model. Results: scenarios where workers did not have protective titles after vaccination or were unaware of the serological status and were exposed to a positive or unknown source-person for hepatitis B. Conclusion: the direct cost of hepatitis B prophylaxis, including confirmation of serological status after vaccination would be more economical for the health system.


Introduction
In the world, approximately 257 million individuals live with chronic hepatitis B virus (HBV) infection (1) . It is known that the cost of treating this disease is high (2)(3) .
In Brazil, 233,027 confirmed hepatitis B cases were reported in the period from 1999 to 2018, with detection rates of 6.7/100,000 inhabitants in 2018, in which 0.3% of the transmission occurred through the occupational route (4) .
In view of the risk of exposure to HBV, the main preventive measure is the vaccination (10) . In Brazil, the Unified Health System (SUS -abbreviation in Portuguese) bears the costs of the HBV vaccine within the National Immunization Program, making it available free of charge since 1998 (11) .
The vaccine is safe and effective, ensuring 92% protection for immunocompetent adults (12) . Despite the high protection, it is recommended after vaccination to perform antibodies against surface antigen (anti-HBs) to confirm immunity to the virus (10) .
Unlike the HBV vaccine, the anti-HBs test is not routinely available in the public health system after vaccination in Brazil.
In handling the accident with biological material, considering the recommendations of the Centers for Disease Control and Prevention (CDC) (10) and the Ministry of Health in Brazil (13) , evaluation of vaccination history and serological status is required for the hepatitis B of HCW and HBV serological status testing for hepatitis B by the surface antigen (HBsAg) from the known sourceperson at the time of occupational exposure.
After this assessment at the time of the accident, four approaches can be adopted considering the In the last three aforementioned conducts, the injured worker must perform the anti-HBs test after the vaccine one to two months after the last dose and after four to six months of this immunoglobulin (10) .
The management of accidents with biological material among HCW is expensive in several countries, mainly in percutaneous exposures (14)(15)(16)(17)(18) . Although the performance of the anti-HBs test among these workers is a recommendation of the Ministry of Health and Labor through the Regulatory Norm (NR) 32/2005 (19)(20) and the CDC (10) , it is known that a considerable part of the vaccinated HCW ignore the serological status for the HBV (5,(21)(22)(23) . Ignoring this status at the time of the accident with a positive source-person requires a high-cost intervention with immunoglobulin, which would turn expensive the post-exposure handling related to the HBV (15) .
In the economic studies, the direct cost involves technology costs for health interventions, including drugs and exams (24)(25) . The evaluation of costs in the health area is increasingly present in the management of health services; therefore, good quality scientific evidence on costs and health outcomes helps in the decision-making (26) .
Since the post-vaccination anti-HBs test is not routinely offered to the worker free of charge by SUS, it was asked what is the lowest cost related to occupational exposure to HBV?
In this sense, the aim of this study was to compare the direct cost, from the perspective of the Unified Health System, of assessing the post-vaccination serological status with post-exposure management for hepatitis B among health care workers exposed to biological material.

Method
Cross-sectional, descriptive and partial economic evaluation study, focusing on the direct cost of    The cost of the vaccine was not considered in this study for economic analysis, as it was assumed that it would not bring financial impact, since this cost is predicted by the SUS for all HCW (11) .
Epidemiological data were processed and analyzed by Statistical Package for the Social Sciences (SPSS ® ), version 20.0 using descriptive statistics. The following criteria were considered for data analysis based on the CDC recommendation (10) : • Vaccinated HCW -those who received the three doses of hepatitis B vaccine reported by the worker; • Non-vaccinated HCW -those who did not receive the three doses of the vaccine, vaccine situation ignored and without information; • HCW with protective titers to HBV -those with anti-HBs test >10 IU/ millilitres (ml); • HCW without protective titers to HBV -those with anti-HBs test; • Unknown source-person -those with inconclusive HBsAg test, not performed, ignored and without information, whose management, recommended by the CDC (10) , is the same for those with positive HBsAg; • Vaccinated HCW and with unknown anti-HBs testthose with inconclusive test, not performed, ignored or without information.
• For the cost analysis of IGHAHB, the prescription of 500 IU was considered as the standard dose, since it is the minimum dosage prescribed for adults (32) .
The economic analysis used was the decision tree model; this graphic representation begins from the left with a decision node, which is divided into branches that propose to evaluate comparatively. In each branch, the probabilities of events must be described until the final event. Therefore, a series of probability nodes appear in each branch. At the end of these branches, the outcomes are presented as terminal node, indicating the final impacts of each branch with their respective costs associated with each analyzed event (33)(34) .
The approach used for the analysis was macrocosting or some top-down method, which allows for a cost analysis of secondary data retrospectively (24) .         the safety of workers, as it will demonstrate the immunological status for the HBV (10, 13) . In Brazil, the rate of carrying out this test after primary vaccination in this group varied between 30.4% (45) ; 27.9% (23) and 4.1% (36) . Brazil, in which the rate of anti-HBs testing among HCW exposed to biological material, in the accident time, ranged from 14.6% to 52.8% (21)(22)(23)(30)(31)47) .
Regarding the serologic status of the source-person for HBsAg positive, a rate of 1.8% (95% CI 1.0 -3.2) was observed in this study. Rate of 0.5% to 1.4% (21,(30)(31) were identified in the literature.
In Scenario A (Figure 1), it was observed that four HCW with anti-HBs <10 IU/ml were exposed to
Regarding age group, there was verified, in accordance with other researches (39)(40) , higher prevalence of young adult workers.
As for the health team, the nursing team corresponds to the largest number of professionals in the health services, being the one who first assists the patient and is present from the admission to the discharge (41) , is responsible for numerous procedures (41) , which is why the higher incidence of accidents is inferred.
As identified in other researches (21,29,37,(42)(43) , in this study, it was identified that the most frequent object in accidents was the needle with and without lumen, therefore exposure to sharp objects prevailed, followed by exposure to mucous membranes. Exposures involving blood were the most numerous, as found in studies in the state of Goiás (36,44) , in other Brazilian states (6,21,42) and in other countries (7,29,37) . Together, the data characterizes a population that should be the target of accident prevention campaigns and the need for investments in professional training to reduce biological occupational risk.  (20) .
Although the vaccine is provided free by SUS, in this study, it was observed that there are still HCW without vaccination, according to scenario B ( Figure 2).
Therefore, it would be important for managers to provide effective strategies to ensure vaccine completion for workers prior to admission to the health service (49) .
In scenario B (Figure 2 (Table 1). Thus, the opportunity to allocate resources to other programs, including those aimed at the health of the own workers, is lost (20) . A Brazilian study showed that HBV infection has high costs for the health system, with an average annual cost per patient of U $ 117 to 11,488 depending on medication (2) , without mentioning the costs of carrying out tests for the clinical and laboratory monitoring of the injured worker. The cost for treating hepatitis B is also high in other countries (50)(51) .
Therefore, when the health system pays for preventable disease treatments, the opportunity to invest in effective prevention and promotion measures is lost (52) . Such analysis can be performed through the opportunity cost, which represents the cost of losing the opportunity to apply financial resources in other health technologies or programs that have a positive impact on public health (53) .
This study showed that the allocation of SUS resources to preventive measures, including the provision and monitoring of anti-HBs tests to all HCW, is more economical than post-exposure management and these data can support public policies on worker health, ensuring greater security at a lower cost. Some gaps found in the SINAN-NET database were its limitation.

Conclusion
The direct cost of post-exposure prophylaxis for SUS was about 30 times more expensive than the costs of post-vaccination testing in those accidents in which the source-person was positive or unknown and the professional had unknown anti-HBs.
for post-exposure management to HBV when compared to scenario D, which represents the primary vaccination followed by confirmation of immunity confirmed by the anti-HBs test, showed greater per capita cost impact.
Health managers can rely on the findings of this study for the implementation of the routine of carrying out the post-vaccination anti-HBs test, ensuring greater protection to the health of the worker with a reduction in the costs of post-exposure management related to HBV, optimizing scarce public resources in our country.