More than five decades have passed since the identification of the etiologic agent of hepatitis B and yet this infection is a challenge for public health worldwide. The development and availability of the first hepatitis B vaccines, still in the 1980s, was a milestone for the prevention of the hepatitis B virus, and currently known as the gold standard strategy for the elimination of this infectious disease.

In several countries, the introduction of the immunobiological occurred gradually, by age groups and risk groups, and in general, started with newborns and children. This universal immunization strategy has contributed to reducing the incidence and changing the epidemiological profile of HBV worldwide. At the beginning of the 21st century, it was already possible to shift the epidemiological curve of the infection to parasitize with 50 years or more. On the other hand, despite vaccination against hepatitis B being the most assertive tool for the prevention of HBV, the low performance of the vaccine in older groups remains a challenge for public health and the object of this study. To our knowledge, there are no data showing the efficacy of doses of enhanced hepatitis B vaccines for older adults, and the purpose of this study is to investigate and compare the immunogenicity of the hepatitis B vaccine in adult adults aged 50 years and over, using conventional doses (20μg) versus (vs) booster doses.

More than five decades have passed since the identification of the etiologic agent of hepatitis B and yet this infection is a challenge for public health worldwide. The development and availability of the first hepatitis B vaccines, still in the 1980s, was a milestone for the prevention of the hepatitis B virus, and currently known as the gold standard strategy for the elimination of this infectious disease.

In several countries, the introduction of the immunobiological occurred gradually, by age groups and risk groups, and in general, started with newborns and children. In Brazil, only in 2015, a free offer of the hepatitis B vaccine expanded a population aged 50 years or older. This universal immunization strategy has contributed to reducing the incidence and changing the epidemiological profile of HBV worldwide. At the beginning of the 21st century, it was already possible to shift the epidemiological curve of the infection to parasitize with 50 years or more.

Consider this scenario of vulnerability to HBV in older adults, it is important to highlight some aspects. The increase in life expectancy around the world is real data and must be evaluated. In addition, contemporary aging is accompanied by an increase and improvement in sexual performance, overcoming myths about "asexual old age" and outdated stereotypes about sexuality for an adult population in the middle and late stages. On the other hand, sexual risk behavior in older people being observed, including unprotected sexual intercourse, multiple sexual partnerships, sexual intercourse with a sex worker, among others. Studies have been increasing the high prevalence of Sexually Transmitted Infections, especially hepatitis B in the elderly.

Given this situation, hepatitis B vaccination is the most assertive tool for preventing HBV. However, even in countries that expand the offer of the vaccine to the entire population, poor performance of the hepatitis B vaccine in older groups remains a challenge for public health and is the object of this study.

A study conducted by Meeren and collaborators, characterized the relationship age vs. age. vaccine response to hepatitis B in immunocompetent adults. The protection index identified, considering all age groups, was 94.5%. However, there was a continuous reduction in seroprotection associated with age, ranging from 98.6% for young adults aged 20-24 years to 64.8% for the elderly (≥65 years). In addition, this study suggested that the aging of the immune system starts in adulthood and is intensified after 50-60 years of age.

In the United States, research conducted with competence aged ≥50 years, showed lower rates of seroconversion compared to younger people, with protection rates ranging from 68% to 82.2%. Another study carried out in this country, elucidated the risk of non-response to the anti-HBV vaccine in 63% for products ≥40 years old (p = 0.046).

Finally, in Brazil, an investigation conducted by Caetano et al. with settlers in Goiás, also illustrated a low responsiveness to the hepatitis B vaccine in the older population. In the age group aged 40-49 years, seroprotection was identified in only 61.9% of the participants, and for the age group aged 50-59 years the rate of seroresponse was even lower, only 55.9% protective titles of anti- HBs. Another study with this same population in Mato Grosso do Sul, showed an average age above 40 years for our non-responders.

Thus, the program that supplants this limitation is necessary, until the cohort of children immunized at birth from a late adulthood. The use of third generation vaccines for this population seems to be difficult to implement due to the high cost of this immunogen. In this way, more frequent or more concentrated doses of the second generation vaccine can be a safe alternative for the older population.

To our knowledge, there are no data showing the efficacy of doses of enhanced hepatitis B vaccines for older adults, and the purpose of this study is to investigate and compare the immunogenicity of the hepatitis B vaccine in adult adults aged 50 years and over, using conventional doses (20μg) versus (vs) booster doses.

Inclusion Criteria:

• person is 50 years of age or older.

Exclusion Criteria:

• people with chronic renal failure, cancer and HIV / AIDS, using corticosteroids;
• people with a history of hepatitis B vaccination (vaccination record of hepatitis B vaccine doses or previous report of hepatitis B vaccination);
• people who are positive for anti-HBs and / or total anti-HBc serological markers.