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A Hib immunization is a shot that helps protect against infection by Haemophilus influenzae type b (Hib) bacteria. It typically works by prompting the immune system to create antibodies against the bacteria, which can help a person fight off infection should he or she later come in contact with the bacteria. Usually given as a series of shots, Hib immunization is typically recommended during early childhood, as children under age five are most at risk for Hib infection. While generally considered safe for most people, there is a chance of experiencing certain side effects from a Hib immunization and there are certain people for whom experts do not recommend it.
As with most vaccines, a Hib immunization aims to mimic the body’s natural immune response. When a person becomes infected with Hib, his or her immune system creates special antibodies designed to help fight back against the bacteria, though serious health problems, such as meningitis, pneumonia, and even death, can occur as the bacteria spread throughout the body before this immune response fully kicks in. A Hib immunization can help prevent such complications by prompting the body to create Hib antibodies before an infection actually exists. It does this by introducing a small amount of inactive Hib into the body, which prompts the immune system to create the targeted antibodies but doesn't actually cause Hib infection. If a person later comes in contact with Hib, he or she should be able to avoid getting seriously ill because the immune system will be able fight off the bacteria from the start.
The Hib immunization series is usually given during early childhood. This is because Hib most commonly affects children under age five. To ensure lasting immunity against Hib, health-care providers generally recommend children receive several doses of the vaccine administered over a period of about a year, often starting around two months of age. There are several versions of the Hib vaccine, and the exact number and timing of needed doses may vary depending on the version used. In addition to young children, experts may also recommend the Hib immunization series for people with weakened immune systems, such as those who have HIV or who are taking chemotherapy.
Many people who get a Hib immunization experience no side effects. If side effects do occur, they are usually mild and may include low-grade fever and swelling where the shot was given. In rare cases, serious side effects, such as allergic reaction, seizures, and trouble breathing, may occur. Experts generally recommend against further doses of the Hib vaccine in people who have had an allergic reaction. They also generally recommend against giving a Hib immunization to children who are less than six weeks old and people who are more than mildly ill at the time vaccination is being considered.