The Haemophilus influenzae type B vaccine, also known as Hib vaccine, is a vaccine used to prevent Haemophilus influenzae type b (Hib) infection. In countries that include it as a routine vaccine, rates of severe Hib infections have decreased more than 90%. It has therefore resulted in a decrease in the rate of meningitis, pneumonia, and epiglottitis.

It is recommended by both the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC). Two or three doses should be given before six months of age. In the United States a fourth dose is recommended between 12 and 15 months of age. The first dose is recommended around six weeks of age with at least four weeks between doses. If only two doses are used, another dose later in life is recommended. It is given by injection into a muscle.

Severe side effects are extremely rare. About 20 to 25% of people develop pain at the site of injection while about 2% develop a fever. There is no clear association with severe allergic reactions. The Hib vaccine is available by itself, in combination with the diphtheria/tetanus/pertussis vaccine, and in combination with the hepatitis B vaccine, among others. All Hib vaccines that are currently used are conjugate vaccine.

An initial Hib vaccine consisting of plain (unconjugated) type b polysaccharide, was introduced in the United States in 1985. but was replaced by a more effective conjugated formulation beginning in 1987. As of 2013^[update], 184 countries include it in their routine vaccinations. It is on the World Health Organization's List of Essential Medicines.

Hib conjugate vaccines are effective against all manifestations of Hib disease, with a clinical efficacy among fully vaccinated children estimated to be between 95–100%. The vaccine has also been shown to be immunogenic in patients at high risk of invasive disease. Hib vaccine is not effective against non-type B Haemophilus influenzae. However, non-type B disease is rare in comparison to pre-vaccine rates of Haemophilus influenzae type B disease.

Before the introduction of the conjugate vaccine, Hib was a leading cause of childhood meningitis, pneumonia, and epiglottitis in the United States, causing an estimated 20,000 cases a year in the early 1980s. Nearly all Hib disease was in children under five years old. After routine use of Hib conjugate vaccines in the United States, the rate of invasive Hib disease decreased from 40–100 per 100,000 children down to fewer than 1 per 100,000. Similar reductions in Hib disease occurred after introduction of the vaccine in Western Europe and developing countries. However, in recent years. Haemophilus influenzae strains with other encapsulated serotypes such as a or f, or non-encapsulated strains, have been recognized to cause invasive disease, particularly in high-risk populations.

The CDC and the WHO recommend that all infants be vaccinated using a polysaccharide-protein conjugate Hib vaccine, starting after the age of six weeks. The vaccination is also indicated in people without a spleen.

Clinical trials and ongoing surveillance have shown the Hib vaccine to be safe. In general, adverse reactions to the vaccine are mild. The most common reactions are mild fever, loss of appetite, transient redness, swelling, or pain at the site of injection, occurring in 5–30% of vaccine recipients. More severe reactions are extremely rare.^{[citation needed]}