In Brazil, as in other countries, national regulations define which diseases are of compulsory notification and how to report them to the official notification system. Infection diseases surveillance systems are essential to guide health politics on national and regional scales but have limitations due to under notification. Several different reasons contribute to this, like failure in diagnosing the disease, in reporting the occurrence of disease to local health authorities, in limited technical or administrative structures, limiting the information flow between local and national systems, among others 20,21.
Under notification may lead to under estimations of the true incidence or prevalence of a given disease. However, a careful analysis of the reported cases allows the identification of space, time and/or age related variations in the notification rate that can indicate changes in infection dynamics 21.
The Brazilian viral hepatitis notification system exists since 1998. During implantation, from 1998 to 2004, several improvements occurred allowing a better performance of the system as a whole. From 2007 to 2018, the system became stable and, consequently, changes in epidemiologic parameters of HBV infection may reflect changes in real infection dynamics.
Trend analysis estimates that Brazilian HBV incidence are stable from 2007 and 2018, but decreases among individuals younger than 39 years from 2013 onwards. In addition, incidence of Acute cases decreased for all age groups in the analyzed period (Fig. 1). Brazilian vaccination program and control measures improvement are probable explanations for these two findings.
In 1989, Brazilian National Vaccine Program initiated Hepatitis B routine vaccination for children (younger than ten years old) living in the endemic Amazon region 22. In 1998, it implemented nationwide Hepatitis B newborn vaccination, with three doses at 0, 1 and 6 months of age, achieving nearly 98% of vaccine coverage in the following years 23,24. From 2003 on, the program expanded to reach people under 49 years old and in 2016 became universal, meaning that any individual have access to HBV vaccination offered by SUS. In addition, susceptible pregnant women are vaccinated on their first pre-natal consultation or at delivery together with the newborn.
In addition, other important hepatitis control measures adopted by Brazilian Health Authorities derive from the HIV/AIDS Brazilian control program, promoting safer sex practices and delivering condoms syringes and needles, under certain conditions, to at risk populations since early 2000 24.
The effects of nationwide vaccination program and control measures in the incidence of HBV infection is also described in countries that, as Brazil, implemented Hepatitis B vaccination program around the year 2000 25.
As mentioned in Results, the proportion of Chronic, Acute and Resolved cases differs greatly among regions. South and Northeast regions have the largest proportions of Chronic cases. This results deviates from the national proportion of Chronic cases and suggests that the burden of HBV Chronic infection is greater in this regions, in the sense that, chronic infections leads to chronic liver disease.
As long as chronic Hepatitis B is considered, the notification increase for those above 40 years-old seen from 2007 to 2018 in Brazil has also been described in China and USA 25,26. As discussed in those articles, the improvement of healthcare can explain these findings as it facilitates diagnosis and decreases mortality rates associated with chronic hepatitis B complications, such as liver cancer and cirrhosis 27.
Similarly to those countries, Brazil has also experienced a reduction in mortality rates of cirrhosis and liver cancer in the last decade 27,28 consequently increasing life expectancy of the chronically infected. This is a direct consequence of the investment increase in Hepatitis B care 23, granted by Brazilian government, comprising access to testing, consultation with hepatitis specialists, antivirals delivery, and laboratory and image follow-ups.
However, the hepatitis B program are limited and, therefore, can diagnose and treat yearly only a fraction of people chronically infected with hepatitis B. Moreover, untreated chronically infected people may infect new partners who can evolve to unnoticed chronic infections. In addition, there is a suggestion that HBV vaccination immunity can wane after long periods of time 29, what could contribute to a further increase in chronic infection pool. As a result, in spite of reducing this pool every year by the improvement on control program activities, it shall remain with a substantial number of people for the next decades.
As described, individuals from South and Southeast acquire Hepatitis B later in life when compared to the other regions. Also, males and females age-related infection rates in this regions are similar, in contrast to North, Northeast and Central-West regions. South and Southeast regions have lower Gini index, lower infant mortality rate, lower women fecundity rate, higher maternal age at firstborn and higher life expectancy at birth when compared to North, Northeast and Central-West regions 30, 11. This better socio-demographic profile of South and Southeast could explain the patterns described in Fig. 3.
This study have strengths and limitations. As off strengths, the proposed case definitions are less restrictive allowing the analysis of a much larger number of cases, although keeping a strict correlation with official HBV status classification (Table 2). The analysis performed to estimate temporal trends of Hepatitis B reported cases follows the methodology adopted by the NIH National Cancer Institute to estimate cancer trends, which was also applied in infectious diseases, specifically in Hepatitis B, by other authors 26,31. This similarity allows a proper comparison among different world regions.
In addition, the analysis performed in this manuscript highlights the use of gender related age distribution, a parameter rarely explored in literature, but of upmost importance for understanding the infection dynamics in a given population.
Limitations of this work relate to the quality of available data. The Brazilian Viral Hepatitis database includes only a fraction of the total HBV Infected individuals, suffering from under-notification. In addition, many observations are incomplete, while some are duplicated, making troublesome, but extremely necessary, a careful revision of data extracted from SINAN. In addition, even with this careful approach the completeness and correction of data cannot be fully warranted. Notwithstanding, as shown in this work, it is possible to recover significant information on disease dynamics even from such incomplete notification database registries.
The analysis performed in this article demonstrates changes in notification rates of Hepatitis B, possibly reflecting differences in national health politics, vaccination programs and universal access to treatment. In addition, regional differences suggest that North, Northeast and Central-West populations are at higher risk to acquire HBV infection earlier in life and develop chronic infection; therefore, vaccination programs should prioritize these regions. Finally, gender differences points to a higher female vulnerability that have to be taken into account on control programs in the less developed Brazilian regions.