Low hepatitis B vaccination coverage among hepatitis B virus carriers communicants in an eastern Brazilian Amazon city

Objective Hepatitis B virus (HBV), even though it is an immunopreventable disease, represents a serious worldwide public health problem. This study evaluated hepatitis B vaccination coverage and the frequency of infection in HBV carrier communicants 20 years after vaccine implementation in the city of Belém, located in the eastern Brazilian Amazon. Results The study, developed between 2015 to 2018, included 288 (n = 288) communicants of HBV carriers. The analyzed population was 53.5% male, with a mean age of 9.4 years (ranging 4 months to 19 years old and a median age of 10 years). Among the examined samples, no HBV carriers (HBsAg positive) were detected; total isolated anti-HBc was detected in 2.1%; 4.2% were anti-HBc total/anti-HBs and 42% anti-HBs isolated, attributed to vaccination; 41.7% received a complete vaccination schedule (three/four doses) and 58.3% were susceptible to HBV. Although the research did not detect HBV in the studied population, there was presence of infection and a significant number of susceptible individuals.


Introduction
Hepatitis B virus (HBV) has primary tropism by hepatocytes and can produce both acute and chronic infection in humans [1,2]. The HBV can be transmitted by parenteral, sexual and vertical transmission [3]. A significant number of HBV infections occur during adolescence and in young adults, due to unprotected sexual relations, multiple partners, abusive use of alcohol and injectable drugs, tattoos and piercings, normal characteristics of their psychosocial development, assuming behaviors of risk without current or future concerns [4].
The present study aimed to evaluate coverage of the hepatitis B vaccination and the frequency of infection in communicants with HBV carriers, 20 years after the vaccine was implanted in the municipality of Belém, located in the eastern Brazilian Amazon. Specifically, the study sought to evaluate the seroepidemiological situation through serological and molecular surveys, detect prevalence and incidence among communicants of HBV carriers and, if necessary, refer for treatment and evaluate the immune response to the hepatitis B vaccine by referring those susceptible to vaccination.  and HBsAg [6,7].

Materials And Methods
The results were stored in the SAHEP/IEC database and the statistical analyses were conducted using 4 EPIINFO 2007 software, version 7.1.0.6. Data analysis was performed using the BioEstat 5.0 program.
To measure the central tendency, we used the time elapsed between the third / fourth dose of the vaccine and blood collection was done by calculating the average. For statistical inference, the chisquare test was used to analyze the association between the variables: gender, vaccine dose and isolated anti-HBc + serological marker, all using a statistical significance level of 5% (p ≤ 0.05) [8].

Results
During the study period, 288 blood samples were collected after active search in homes of HBV carriers in the neighborhoods of Belém. The highest frequency of sample collection occurred in the neighborhoods of Benguí (11.8%, 34/288); Guamá (11.5%, 33/288), Val-de-Cães ( HBV serological analysis did not detect carriers of the HBV, characterized by the absence of HBsAg. Isolated anti-HBc was detected in 2.1% (6/288) reagent samples; 4.2% (12/288) of the samples examined were total anti-HBc/anti-HBs reagents and 42% (121/288) had isolated anti-HBs reagent, attributed to vaccination, where 73.3% were found in the 1 to 4 years old age group. Statistical significance was found for isolated anti-HBs by performing the chi-square adherence test for equal expected samples, with p (value) < 0.0001 (Table 1).

Discussion
The study conducted by Souto showed that the distribution of HBV infection in Brazil showed the reduction of hepatitis B prevalence in the country, classifying the national territory as low endemicity to HBV [9]. The present study suggested a pattern of low endemicity, identified by the absence of the HBsAg serological marker [10].
During home visits, HBV patients were found living in places with difficult access and in precarious conditions, collaborating with the study of El Khouri, who linked hepatitis B infection to poor living conditions [11].
Study participants were considered at high risk for HBV infection according to behavioral issues, providing them with a sense of invulnerability, which was also perceived by Coutinho in his study on adolescents and hepatitis B vaccine [4]. In the current study, 9% of those examined pointed to lack of interest as the main reason for non-vaccination, although Carneiro et al., cited forgetfulness as the principal reason [12]. 6 The vaccination booklet was characterized as one of the difficulties during the research, considering that 54.9% of respondents did not have proof of vaccination. One of the ways to solve the problem of losses would be to implement an adequate computerized system with information about vaccines, which is compatible with a study by Santos and Oliveira, where they mentioned the lack of a personalized information system as one of the health system problems [13].
The absence of HBV carriers among the participants was in accordance with a prevalence study conducted in the state capitals and the Federal District of Brazil. However, it was expected to find in this study a higher percentage of reactive results, considering that the population was composed of individuals subjected to risk situations [14].
This research identified a rate of 42% (121/288) people with isolated anti-HBs attributed to vaccination, with the highest vaccination coverage of 36.4% in the age group of 1 to 4 years old.
When analyzing the population from 0 to 9 years old, 59.6% of anti-HBs isolated reagent was found, inferior to the previous study that found a higher percentage than 70% of vaccinated children from 0 to 10 years old [9] and also inferior to the study conducted among children and adolescents from Egypt, with complete vaccination scheme that found 57.2% serological protection [15].
Vaccination coverage in the municipality of Belém was heterogeneous for the period analyzed, and below the national average. This was similar to what happened in a study in the city of Trindade, State of Goiás, which obtained unsatisfactory coverage in most years, considering the basis of hepatitis B prevention is the vaccine, which provides 90-95% protection to immunocompetent individuals, with an appropriate vaccination schedule [16, 17,18].
The prevalence of 58.3% of non-vaccinated individuals found in the study conducted in Belém was higher than that found in two municipalities of Parauapebas Microregion, southeast of the state of Pará, where, in the municipality of Canaã dos Carajás, the prevalence of 44.1% was detected, and in the municipality of Curionópolis, 36.4% were found susceptible to HBV [19].
Regarding the age group of children with vaccine delay, the highest prevalence was among children under one year old of age with 66.7%, higher than that found in Carneiro's study that identified 55% for children under the age of six months to one year [12]. 7

Conclusion
The absence of HBV carriers among communicants under 20 years of age suggested that the municipality of Belém has low endemicity for this group.
The home visiting team found it difficult to collect material due to the fragility of the public safety system, frequent changes of address and factors associated with misinformation.
Among the survey participants, 58.3% had not completed the full vaccination schedule. They had negative results for the anti-HBs test and had never previously had the test performed. Thus, the research suggests the need for incremental continuing education programs in schools and intra-family control.
These results allowed us to infer the need for greater attention and control of communicants, free consent for the use of their data, scientific evaluation and publication.

Consent for publication
Not applicable.

Availability of data and materials
All data generated or analyzed during this study is included in this published article. Samples are available from the corresponding author upon reasonable request.