What is hepatitis B?
Hepatitis B virus (HBV) is a member of the Hepadnaviridae (hepa – Greek for liver, dna – the type of genetic material it has, viridae – Latin for virus) family. HBV infections can be symptom-free, cause short-term symptoms, or cause chronic disease. In the initial phase, symptomatic infections are characterized by fever, chills, fatigue, decrease or loss of appetite, nausea, abdominal pain and/or jaundice. Initial complications can also include kidney inflammation, low platelet counts, joint pain and swelling, and rash. Chronic forms of HBV infection are associated with permanent scarring (i.e. cirrhosis, 12-20%), failure (20-23%), or cancer (i.e. hepatocellular carcinoma, 6-15%) of the liver.
HBV is a sneaky virus because it is durable, highly contagious, and can infect people [and still be spread] without causing symptoms for years.
- HBV can remain stable and infectious in dried blood at room temperature for weeks on common surfaces (e.g. tables/chairs at restaurants, shopping carts, staircase handrails, etc).
- Because there are between 100 million and 10 billion infectious virus particles per 1 mL of blood contaminated with HBV, new infections can be caused by amounts of blood not seen by the naked eye.
- Symptom-free infections are more common under age 30 than symptomatic infections. Being symptom-free increases the risk of spreading the virus without knowing you have it.
- More than 99% of infected infants less than 1 year are symptom-free
- 85-95% of infected children between 1 and 5 years old are symptom-free
- 50-70% of infected individuals 6 to 30 years old are symptom-free
- Data are not available for adults older than 30 years old with symptom-free HBV
How does someone get HBV?
HBV is spread through contact with infected blood or body fluids, such as amniotic fluid, vaginal secretions, and semen. In adolescents and adults, IV drug use is another possible risk factor for contracting HBV. Contact with infected fluid from other parts of the body is a risk factor almost exclusively limited to medical professionals. While HBV is typically thought of as spread through intimate contact, casual contact through sharing of toothbrushes and razors with infected family members or friends is also possible.
Due to rigorous screening protocols, contracting HBV from a blood transfusion is rare, but does occur at a rate of approximately 1 in 1-1.5 million transfusions. These rare occurrences are typically a result of the donor having recently become infected, but the levels of virus are not yet detectable at the time the blood is screened. Per the Red Cross, approximately 1 in 12,000 donations shows signs of active HBV infection during their screening processes and are consequently not given to patients in need of blood products.
If HBV is typically contracted from sex and IV drug use, how can my baby/child get it?
Vertical transmission from pregnant mother to baby typically occurs at the time of birth but can also occur in utero or after birth. Sometimes pregnant mothers can unknowingly contract HBV close enough to when they are screened during pregnancy that it goes undetected. Other times, the test result for HBV may be a false negative. Testing for HBV is reliable, but it is not perfect.
Babies can also contract HBV from an infected father through casual contact with blood from an innocent scrape, cut or other opening in the skin.
Once they become mobile, older infants and toddlers get into everything. Their curiosity and accident-prone nature put young children at risk for developing open wounds on their skin and touching potentially contaminated surfaces.
What type of vaccine is the HBV vaccine?
The HBV vaccine is a recombinant vaccine. Recombinant vaccines are made by isolating only the DNA that codes for the germ’s specific antigen (e.g. the protein or sugar) our bodies recognize and to which we make antibodies. This isolated DNA code is then put into yeast or bacteria in a lab to produce a lot of the antigen without the germ itself. The recombinant HBV vaccine contains the protein Hepatitis B Surface Antigen (HBsAg). Recombinant vaccines cannot cause actual disease.
Because chronic HBV infection can cause liver cancer, the HBV vaccine was the first cancer-preventing vaccine ever created. We will cover another cancer-preventing vaccine, the HPV vaccine, in a future blog.
When is the HBV vaccine administered?
Because vertical transmission from an unknowingly infected birth mother is a possible exposure source for infants, the first dose is recommended soon after birth, typically in the newborn nursery prior to hospital discharge. Giving the vaccine this early helps to neutralize the virus as quickly as possible in cases of vertical transmission when the birth mother has HBV but doesn’t know it. Note: if the birth mother is known HBV positive, the baby will also receive the pre-made antibody HBIg (Hepatitis B Immunoglobulin) for more immediate neutralization.
The second and third doses of the vaccine series are typically administered 4 weeks after the first, and at the 9-month check-up, respectively. The third dose can be administered as early as 4 months from the second.
What are possible side effects of the HBV vaccine?
Pain at the time of injection is the most common, and often the only, side effect. Infants are quickly consolable after administration, and do not typically have further fussiness. Practicing the 5 S’s (e.g. Sucking/feeding, Swaddling, Shushing, Swaying, Side-lying position (left side-down)) can bring about the quickest resolution of their discomfort and crying. Fatigue is possible but uncommon. Less commonly children may develop redness, swelling or a nodule at the injection site. Fever is even less common than the aforementioned. About 1 in 600,000 recipients can have a severe allergic reaction.
If my child is low-risk, why should I vaccinate them at such a young age?
As with many illnesses, the stakes are higher for younger patients, and more specifically babies. Only 1-5% of adults who contract hepatitis B will go on to develop chronic infection, but nearly 90% of newborns/infants will. As noted above, those with chronic infection are more likely to develop liver scarring, liver cancer, liver failure, and/or need liver transplant. Vaccinating early in infancy lowers the risk of vertical transmission during childbirth and protects children before they reach the mobile, curious and accident-prone stage that puts them at higher risk for potential casual exposure in their everyday environments. When the stakes are high and the risk of side effects of vaccination are extremely low, the potential benefits far outweigh the potential downside.
Why can’t we try a risk-based approach and only vaccinate “high-risk” individuals?
When the first official recommendations for use of HBV vaccine were announced in 1982, the United States used a risk-based approach. The approach had limitations because years of data showed that outside of healthcare workers, other high-risk individuals were either (a) not getting identified (b) not understanding the true risk of HBV infection (c) not knowing a vaccine existed; or (d) didn’t didn’t have access to the vaccine. In 1991, universal infant vaccination was recommended in an effort to protect the population that is most likely to go on to develop chronic hepatitis B and its complications. Prior to 1991, the rates of acute HBV infection in infants and children had not changed significantly with the risk-based approach. Ever since, there has been a dramatic drop in pediatric HBV infections (see chart below from the 2002 MMWR Weekly report).
Hepatitis B screening during pregnancy remains an important tool for assessing risk to infants, but no test can detect 100% of cases. Additionally, a mother could contract HBV after the testing is done. Other household members who could be infected, but aren’t typically symptomatic or tested, can be exposure sources that increase a child’s risk.
What’s the problem with testing antibodies after each vaccine dose to see whether my baby needs the full series or not?
(1) This is unnecessary pain for the child. Pediatricians share a desire with parents for the least necessary painful experiences. 1 injection and 1 blood draw per vaccine is excessive and unnecessary when the benefit and safety profile is already extremely well documented in trial data and after market studies. Additionally, young infants veins are so small that it may take several needle poke attempts to find an adequate vein from which to draw the blood to test for antibodies
(2) The clinical significance of antibody levels after just 1 or 2 doses of vaccine has not been validated. At this time there isn’t evidence that those antibody levels stay elevated long-term, as is the case after the 3 dose series. Consequently, having evidence of an adequate antibody response at, say, 1 or 2 months old, and not further vaccinating will necessitate blood drawn regularly to ensure the antibody levels stay elevated above a protective level.
(3) There is no evidence that administering children 2nd and 3rd doses causes more side effects. 3 doses, as recommended, is as safe as 1 dose.
References
Than TT, Jo E, Todt D, Nguyen PH, Steinmann J, Steinmann E, Windisch MP. High Environmental Stability of Hepatitis B Virus and Inactivation Requirements for Chemical Biocides. J Infect Dis. 2019 Mar 15;219(7):1044-1048. doi: 10.1093/infdis/jiy620. PMID: 30358855; PMCID: PMC6420165.
Stramer SL, Notari EP, Krysztof DE, Dodd RY. Hepatitis B virus testing by minipool nucleic acid testing: does it improve blood safety? Transfusion. 2013 Oct;53(10 Pt 2):2449-58. doi: 10.1111/trf.12213. Epub 2013 Apr 23. PMID: 23607261.
https://www.redcrossblood.org/biomedical-services/blood-diagnostic-testing/blood-testing.html
https://www.hepb.org/prevention-and-diagnosis/vaccination/
https://vaccineknowledge.ox.ac.uk/types-of-vaccine#Subunit-Vaccines
Centers for Disease Control and Prevention. Achievements in public health: hepatitis B vaccination — United States, 1982–2002. MMWR Weekly. 2002;51(25):549-552.