Hepatitis B 2020-2021 - acute and chronic
Acute and chronic hepatitis B 2020 and 2021
Acute hepatitis B
In 2020, the Department of Infectious Epidemiology and Prevention received 14 notifications of acute hepatitis B. The corresponding figure for 2021 was six notifications.
The number of notified cases of acute hepatitis B remains low, even though more acutely infected persons were observed in 2020 than in 2021, Figure 1. The majority of the acute cases in 2020 and 2021 had become infected by sexual transmission. In both years, all cases had become infected in Denmark. The median age was 46 years (range: 28-65 years) in 2020 and 52 years (range 32-56 years) in 2021. For the first time since 2016, 2020 saw notified cases of acute hepatitis B who had become infected by IV drug use. This underpins the importance of routine testing of IV drug users in order to be able to offer vaccination control and treatment of hepatitis B in this group. Even so, the number of cases was very low (the exact figure cannot be provided for GDPR reasons).
In the Danish Health Authority’s guideline on HIV and hepatitis B and C, you will find more information about vaccination recommendations and testing along with a list presenting the risk groups offered a free vaccination schedule in Denmark.
Chronic hepatitis B
In 2020, the Department of Infectious Disease Epidemiology and Prevention received 139 notifications of chronic hepatitis B. The corresponding figure for 2021 was 118 notifications. The number of persons notified with chronic hepatitis B in 2020 and 2021 followed a declining trend, Figure 1.
In 2020 and 2021, the majority of cases of chronic hepatitis B were immigrants who were infected prior to their arrival to Denmark. The majority were notified as mother-to-child-transmission; and for most of the remaining cases, the mode of infection was unknown (number not published for GDPR reasons).
In 2020, 92 of the notified cases (66%) were women. The median age for women was 33 years (range: 9-79 years); for men it was 39 years (range 25-69 years).
In 2021, 76 of the notified cases (64%) were women. The median age for women was 33 years (range: 20-73 years); for men it was 38 years (range 21-75 years).
More than half of the women notified with chronic hepatitis B were detected via the general screening of pregnant women. No children in Denmark were notified as having become infected at birth in 2020 or 2021. Every year, screening of pregnant women for hepatitis B detects a considerable number of asymptomatic carriers all of whom must be referred to a specialist department for further check-up, control and treatment, if relevant. Children born by hepatitis B positive mothers must receive immunoglobulin and vaccination at birth (so-called post-exposure vaccination), see Vaccination of children born by women with chronic hepatitis B infection.
The number of notifications with chronic hepatitis B infection depends on various factors, including, among others, testing frequency and notification percentage, and immigration from countries with a high occurrence of hepatitis B. According to Statistics Denmark, the total immigration to Denmark declined from 2019 to 2020 (from approx. 86,000 to 72,000, 16%) and only increased slightly in 2021. This may contribute to explaining part of the decline observed in the number of notified cases.
No reasons seem to suggest that the notification percentage will continue to follow a declining trend. However, in 2020 and 2021, the COVID-19 epidemic may have affected the testing frequency.
Not all hepatitis B test results are reported to the MiBa (only those tested at departments of clinical microbiology). Therefore, Statens Serum Institut cannot determine if the testing frequency had declined in the years in question.
As the number of persons notified with hepatitis B in 2020 and 2021 has been low, data protection provisions make it impossible to publish an annual report detailing modes of infection and other detailed items of information. Anyone meeting the legal requirements to access the detailed information may request data access by contacting lheh@ssi.dk.
(L. H. Holm, S. Cowan, Department of Infectious Disease Epidemiology and Prevention)
21 December 2022