▎WuXi AppTec content team editor
In 2016, the World Health Organization (WHO) set a target of "a 90% reduction in the incidence of viral hepatitis and a 65% reduction in viral hepatitis-related mortality by 2030". According to 2019 statistics, there are about 1.5 million new cases of chronic hepatitis B and 820,000 chronic hepatitis B-related deaths worldwide, and much more needs to be done to achieve the WHO targets.
Since the prevention of hepatitis B is of great significance to achieve the goal of reducing the incidence of the disease, this article focuses on hepatitis B prevention in infants and young children, hepatitis B prevention in adults, and how to avoid mother-to-child transmission of hepatitis B virus in pregnant women.
Screenshot credit: The Lancet
Up to 90% risk of infants and young children progressing to chronic infection
In 2019, approximately 296 million people worldwide tested positive for hepatitis B surface antigen (HBsAg), and the global prevalence of chronic hepatitis B was approximately 3.5%. Although the prevalence of chronic hepatitis B varies greatly in different parts of the world. However, the incidence of acute hepatitis B infection and the prevalence of chronic hepatitis B infection are currently declining, particularly in children and young adults (mainly related to universal vaccination of infants and young children).
Non-immune individuals who have broken skin or mucous membranes may become infected with HBV after accidental exposure to blood, semen, or saliva from people infected with HBV. Hepatitis B virus usually survives outside the body for 7 days or more and is more contagious than HIV. Hepatitis B virus can be detected in breast milk, but there have been no reports of hepatitis B transmission from infants fed breast milk (HBsAg-positive mothers).
The most common modes of transmission of HBV include sexual contact, perinatal/vertical transmission of HBsAg-positive mothers to newborns, and horizontal transmission within the family (especially in children) of infected people through occult parenteral exposure (presumably open incisions or ulcers). It is worth mentioning that the risk of progression from acute to chronic infection in patients with hepatitis B infection is inversely proportional to the age at the time of infection, specifically, infants and young children infected with hepatitis B have a risk of progressing to chronic infection of about 90%; 20% for children; Less than 5% of immunocompetent adults.
People with HBV infection may also be co-infected with other viruses (through the same mode of transmission). HDV is a deficiency virus and can only infect people who are HBsAg-positive. It is estimated that HCV infection currently affects approximately 5% of people living with hepatitis B worldwide. In the population of hepatitis B patients, about 1%~15% have hepatitis C virus infection; 1%~2% have HIV infection.
In addition, as patients with chronic hepatitis B age and the number of comorbidities increase, the risk of liver and non-hepatic complications increases.
Some adults may also need to be vaccinated against hepatitis B!
Vaccination is the most effective way to prevent hepatitis B infection. Recombinant HBV vaccine has considerable safety and high protection, and can be administered not only as a single vaccine or as a combination vaccine in newborns, but also as a combination hepatitis A and B vaccine in people of all ages.
Age and immunity are key factors affecting the immunogenicity of vaccination, while factors that reduce the protective effect of vaccines include: obesity, smoking, genetic factors, and some comorbidities (such as chronic renal failure, chronic liver disease, diabetes).
Given the high risk of disease progression to chronic infection in infants and young children after HBV infection, universal infant vaccination would be the most effective means of preventing chronic HBV. As of 2020, about 98% of countries in the world have adopted a universal infant hepatitis B vaccination strategy, it should be noted that although the coverage rate of 3~4 doses of vaccine for infants and young children has reached 83%, the timely coverage rate of the vaccine at birth is still less than 50%.
The prevalence of hepatitis B in children under 5 years of age has fallen from 4.7% before 2000 to less than 1% after 2016. For high-risk susceptible adults, vaccination against hepatitis B is also necessary to reduce the risk of hepatitis B virus infection. In 2022, the United States expanded the range of people eligible for hepatitis B vaccination to include all people under 60 years of age and those 60 years of age or older seeking protection. It is worth noting that two new recombinant vaccines (HepB-CpG vaccine and PreHevbrio vaccine) have recently been licensed for adult use in the United States and the European Union, which can improve the responsiveness of people over 60 years of age or immunocompromised.
It is important to note that although hepatitis B surface antibody levels will gradually decrease over time, the protective effect after vaccination appears to last for 30 years or more due to the presence of immune memory. Therefore, booster doses are not currently recommended in healthy, fully vaccinated children or immunocompetent adults.
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Can breastfeeding transmit hepatitis B?
The combined active and passive immunoprophylaxis of neonates has an overall efficacy of nearly 95% in interrupting mother-to-child transmission of hepatitis B virus. In addition, antiviral therapy in pregnant women with hepatitis B infection in the third trimester further reduces the risk of mother-to-child transmission of hepatitis B virus. Specifically, combined active- and passive immunoprophylaxis strategies for newborns include:
All pregnant women are screened for HBsAg, with HBsAg-positive HBV DNA levels measured. Patients with HBV DNA levels exceeding 200000 IU/mL should receive tenofovir disoproxil fumarate from the 24~32nd week of pregnancy, and can stop treatment immediately after delivery or continue treatment for 12 weeks; After that, the serum alanine aminotransferase (ALT) level was monitored every 1~3 months for 6 months;
1 dose of hepatitis B immune globulin (HBIG) and hepatitis B vaccine within 12 hours of birth;
Newborns are vaccinated against hepatitis B from 1 month of age (3 doses in total).
It is currently recommended to confirm immunity by measuring the level of hepatitis B surface antibodies between the 9th and 15th months of the newborn. Delayed or failed HBIG or birth-dose vaccination and incomplete vaccination may result in mother-to-child transmission of HBV.
The review highlights that by strictly following current recommended interventions, we have every chance of eliminating mother-to-child transmission of HBV. In addition, there is currently no evidence that HBV can be transmitted through breast milk, so breastfeeding should not be discouraged by following precautionary measures.