At birth, newborns in the United States are given two injections into the muscle. One of these injections is the vitamin K injection, which we reviewed in the last lesson. The other injection is the hepatitis B vaccine. In this lesson, let's review information about the hepatitis B virus, and why it is important to vaccinate newborns shortly after birth. Hepatitis B is a virus. Infection with this virus affects the liver as well as many different organs in the body. It is estimated that one third of the world's population or two billion people have been infected by the hepatitis B virus. Certain parts of the world have higher rates of the infection than others as seen on this map. The disease burden in the US is less than in other parts of the world but it is still substantial. How is the hepatitis B virus transmitted to cause infection? The hepatitis B virus is present in most bodily fluids. Blood, semen, and vaginal secretions are some of the most potentially infectious bodily fluids for hepatitis B. Perinatal vertical transmission, meaning transmission of the virus from an infected mother to her baby during delivery is one of the most common ways that this infection can be transmitted. This is because of the exposure to mother's blood, during labor and delivery. A neural transmission, meaning, infection of the fetus during pregnancy is much less common. Another less common, but still irrelevant mode of transmission includes close contact with highly infective individuals. There are other ways that infection can occur, but these are outside of the scope of this discussion. It is important to note that breast-feeding has not been shown to be a risk of transmission of Hepatitis B virus from mother to infant. Risk of transmission of the infection from mother to infant is higher, if the mother has a higher circulating amount of virus in her blood. There are different tests for hepatitis B that can determine whether an infected individual may have high rates of viral replication, and increased risk of infectivity, but our review of these tests is also beyond the scope of this discussion. So, why do we care about infection of newborns with the hepatitis B virus? First, patients that are infected as infants and children have the greatest risk of developing serious complications from this infection, and some are potentially fatal. Infants infected perinatally or almost always asymptomatic with the initial infection, meaning, they do not typically show signs of acute infection after birth. However, they are at greatest risk of becoming chronically infected. It is estimated that 90 percent of infants infected perinatally become chronically infected. This can lead to growth impairment, liver cirrhosis, meaning scarring other severe damage to the liver, or liver cancer later in life. Current treatments cannot remove the virus completely from a person's body. So, it is especially important to try and prevent this infection for our newborn patients. It is important to note that prevention of this infection in newborns starts with routine screening of pregnant women for the hepatitis B infection. This allows for appropriate measures of prevention to be taken once the newborn is delivered. So, it is important to prevent infection of a newborn with hepatitis B to prevent long-term complications from the infection. While it is estimated that 98 percent of vertical transmission are from mother to baby of the infection happens during delivery. This is potentially preventable by administering certain injections after birth. This includes the hepatitis B vaccine for short and long-term protection, and the hepatitis B immunoglobulin or antibodies injection also known as HBIg for short-term protection in certain cases. Without the use of the hepatitis B vaccine and HBIg, the risk of an infant becoming infected with hepatitis B from the mother due to perinatal exposures as high as 70 to 90 percent. The hepatitis B vaccine was approved in 1982 and has been shown to be highly effective in preventing the infection, estimated at 90 to 95 percent effective. The prevalence of chronic hepatitis B infection in children has declined 90 percent since universal hepatitis B vaccination was instituted. Adverse reactions are uncommon. The most common risk is paying around the site of the injection. In order to prevent infection, when should an infant be immunized against hepatitis B? The CDC recommends universal immunization of newborns at birth. This means that the vaccine should be administered to all newborns, whether or not, they are born to a mother with a known hepatitis B infection. The American Academy of Pediatrics or AAP, recommends administration of the hepatitis B vaccine to all newborns born to hepatitis B negative mothers within 24 hours of birth. Infants born to mothers who have an unknown hepatitis B status, should ideally received the vaccine by 12 hours of life. Infants will go on to complete two to three additional doses of the vaccine over the next several months of their life. Newborns born to hepatitis B negative mothers, who weigh less than 2,000 grams should receive the vaccine at one month of age or at the time of discharge from the hospital, whichever comes first, according to the AAP. When an infant is born to a mother who is known to be infected with hepatitis B, the hepatitis B vaccine should be administered within the first 12 hours of birth. They should also receive a concurrent or at the same time, injection of the hepatitis B immunoglobulin, again, HBIg, at a different site of the body than where the vaccine was given. Administering HBIg will provide additional short-term protection against this infection. Again, the initiation of breastfeeding does not have to be delayed while waiting to administer the hepatitis B vaccine and the HBIg. Off-note, if a newborn weighs less than 2,000 grams, but is born to a mother who is hepatitis B positive, the vaccine should be administered within 12 hours along with HBIg as just described. However, this initial hepatitis B vaccine dose does not count towards the completion of the hepatitis B vaccine series. So, three additional doses will still be required in the following months. Infants who are born to mothers infected with hepatitis B will need laboratory testing later in life after they complete their vaccination series. In the US, testing of these infants for hepatitis B is recommended at one to two months after completion of the last vaccine dose, usually around nine to 12 months of age. We have reviewed so much information in this module. You now know why it is important to give the hepatitis B vaccine to newborns, and how to give an intramuscular injection to a newborn. With this knowledge, you will be able to provide care to newborns in order to give them the best possible start to a healthy life.
