Haemophilus influenzae disease is a name for any illness caused by bacteria called H. influenzae. Some of these illnesses, like ear infections, are mild while others, like bloodstream infections, are very serious. In spite of the name, H. influenzae do not cause influenza (the flu). Vaccines can prevent one type of H. influenzae (type b or Hib) disease.

Vaccines Can Protect Your Child from Hib Disease

Hib can cause severe infections of both the lining of the brain and spinal cord (meningitis) and the bloodstream. Vaccines can prevent Hib disease. CDC recommends Hib vaccination for all children younger than 2 years old.

How It Spreads

People can spread H. influenzae, including Hib, by coughing or sneezing while in close contact with others. People around them then can breathe in the bacteria. Even people who are not sick can have the bacteria in their noses and throats and spread the bacteria.

Haemophilus is the name of a group of bacteria. There are several types of Haemophilus. They can cause different types of illnesses involving breathing, bones and joints, and the nervous system.

One common type, Hib (Haemophilus influenzae type b), causes serious disease. It usually strikes children under 5 years old. Your child can get Hib disease by being around other children or adults who may have the bacteria and not know it. The germs spread from person to person. If the germs stay in the child's nose and throat, the child probably will not get sick. But sometimes the germs spread into the lungs or the bloodstream, and then Hib can cause serious problems such as meningitis and pneumonia.

Treatment is with antibiotics. There is a vaccine to prevent Hib disease. All children younger than 5 years of age should be vaccinated with the Hib vaccine.

Haemophilus influenzae is a bacterium that causes often-severe infections, particularly among infants. It was first described by Richard Pfeiffer in 1892. During an outbreak of influenza, he found H. influenzae in patients’ sputum and proposed a causal association between this bacterium and the clinical syndrome known as influenza. The organism was given the name Haemophilus by Charles-Edward Winslow, et al. in 1920. It was not until 1933 that it was established that influenza was caused by a virus and that H. influenzae was a cause of secondary infection.

In the 1930s, Margaret Pittman demonstrated that H. influenzae could be isolated in encapsulated (typeable) and unencapsulated (nontypeable) forms. She observed that virtually all isolates from cerebrospinal fluid (CSF) and blood were of the capsular type b.

Before the introduction of effective vaccines, H. influenzae type b (Hib) was the leading cause of bacterial meningitis and other invasive bacterial disease, primarily among children younger than age 5 years; approximately one in 200 children in this age group developed invasive Hib disease. Approximately two-thirds of all cases occurred among children younger than age 18 months.

A pure polysaccharide vaccine was licensed for use in the United States in 1985 and was used until 1988. The first Hib conjugate vaccine was licensed in 1987.

Quick facts

• Causes severe bacterial infection, particularly among infants
• During late 19th century believed to cause influenza
• Immunology and microbiology clarified in 1930s
• Leading cause of bacterial meningitis during prevaccine era

Haemophilus influenzae, a type of bacteria, can cause many different kinds of infections. These infections range from mild, ear infections, to serious, like bloodstream infections.

Doctors consider some of these infections “invasive.” Invasive disease happens when the bacteria invade parts of the body that are normally free from germs. For example, H. influenzae can invade the spinal fluid, causing meningitis, or bloodstream, causing bacteremia. Invasive disease is usually serious, requiring treatment in a hospital, and can sometimes result in death.

The most common types of invasive disease caused by H. influenzae are:

• Pneumonia* (lung infection)
• Bloodstream infection
• Meningitis
• Epiglotittis (swelling in the throat)
• Cellulitis (skin infection)
• Infectious arthritis (inflammation of the joint)

H. influenzae can also be a common cause of ear infections in children and bronchitis in adults.

*Doctors consider pneumonia an invasive infection when H. influenzae also infects the blood or fluid surrounding the lungs.

H. influenzae, including Hib, disease occurs mostly in babies and children younger than 5 years old. Adults 65 years or older, American Indians, Alaska Natives, and people with certain medical conditions are also at increased risk. Those medical conditions include:

• Sickle cell disease
• Asplenia (no spleen)
• HIV infection
• Antibody and complement deficiency syndromes (rare conditions that affect the body’s ability to fight infections)
• Cancer requiring treatment with chemotherapy, radiation therapy, or bone marrow stem cell transplant

Haemophilus influenzae disease is a name for any infection caused by bacteria called H. influenzae. There are 6 identifiable types of H. influenzae (named a through f) and other non-identifiable types (called nontypeable). The one that people are most familiar with is H. influenzae type b or Hib.

These bacteria live in people’s nose and throat, and usually cause no harm. However, the bacteria can sometimes move to other parts of the body and cause infection.

Experts do not know how long it takes after H. influenzae enter a person’s body for someone to get sick. However, it could take as little as a few days before symptoms appear.

People spread H. influenzae, including Hib, to others through respiratory droplets. This happens when someone who has the bacteria in their nose or throat coughs or sneezes. People who are not sick but have the bacteria in their noses and throats can still spread the bacteria. That is how H. influenzae spreads most of the time.

The bacteria can also spread to people who have close or lengthy contact with a person with H. influenzae disease.

Haemophilus influenzae can cause many different kinds of infections. Symptoms depend on the part of the body that is infected.

Pneumonia

Symptoms of pneumonia usually include:

• Fever and chills
• Cough
• Shortness of breath or difficulty breathing
• Sweating
• Chest pain
• Headache
• Muscle pain or aches
• Excessive tiredness

Bloodstream Infection

Symptoms of bloodstream infection usually include:

• Fever and chills
• Excessive tiredness
• Pain in the belly
• Nausea with or without vomiting
• Diarrhea
• Anxiety
• Shortness of breath or difficulty breathing
• Altered mental status (confusion)

Bloodstream infection from H. influenzae can occur with or without pneumonia.

Meningitis

Symptoms of meningitis typically include sudden onset of:

• Fever
• Headache
• Stiff neck
• Nausea with or without vomiting
• Photophobia (eyes being more sensitive to light)
• Altered mental status (confusion)

Babies with meningitis may be irritable, vomit, feed poorly, or appear to be slow or inactive. In young babies, doctors may also test the child’s reflexes, which can be abnormal with meningitis.

Doctors usually diagnose Haemophilus influenzae infection with one or more laboratory tests. The most common testing methods use a sample of blood or spinal fluid.

Even with appropriate treatment, some H. influenzae infections can result in long-term problems or death. For example, bloodstream infections can result in loss of limbs. Meningitis can cause brain damage or hearing loss.

Complications are rare and typically not severe for bronchitis and ear infections caused by H. influenzae.

People diagnosed with H. influenzae disease take antibiotics, usually for 10 days, to treat the infection. Depending on how serious the infection is, people with H. influenzae disease may need care in a hospital. Other treatments may include:

• Breathing support
• Medication to treat low blood pressure
• Wound care for parts of the body with damaged skin

When H. influenzae cause milder infections, like bronchitis or ear infections, doctors may give antibiotics to prevent complications.

Vaccine

Vaccines can prevent Haemophilus influenzae type b (Hib) disease. However, the Hib vaccine does not prevent disease caused by the other types of H. influenzae. Learn more about Hib vaccination, including who should get vaccinated.

Re-Infection

People can get H. influenzae more than once. A previous Hib infection might not protect you from future infection. Therefore, CDC recommends Hib vaccination even if someone has had Hib disease in the past.

Preventive Antibiotics

H. influenzae can spread to people who have close or lengthy contact with a person with H. influenzae disease. In certain cases, close contacts of someone with H. influenzae disease should receive antibiotics to prevent them from getting sick. A doctor or local health department will make recommendations for who should receive preventive antibiotics.

Make sure your child gets all shots of Haemophilus influenzae type b (Hib) vaccine for protection against Hib disease. Hib vaccines protect young children when they are at highest risk of getting Hib disease and having serious complications.

Vaccines can prevent disease caused by Hib, but not the other types (“strains”) of H. influenzae bacteria. The best way to prevent Hib disease is to get vaccinated.

CDC Recommends Hib Vaccines for All Young Children and Certain Other People

CDC recommends Hib vaccination for all children younger than 5 years old. Children need multiple (3 or 4) shots of a Hib vaccine. CDC recommends shots at the following ages:

• 2 months
• 4 months
• 6 months (if needed; depends on brand)
• 12 through 15 months

Call your child’s doctor if you have questions and to make sure your child received all recommended doses.

Older children and adults usually do not need a Hib vaccine. However, CDC recommends Hib vaccination for people with certain medical conditions. Talk with your or your child’s doctor if you have questions about Hib vaccines.

All children should get the full series of Hib shots as babies and need one booster shot when they are 12 through 15 months old.

Hib Vaccines Are Safe

Most children who get a Hib vaccine do not have any problems with it. However, side effects can occur. Most are mild, meaning they do not affect daily activities, and get better on their own in a few days. Mild side effects can include fever or redness, warmth, or swelling where the doctor gave the shot. See the Hib vaccine information statement to learn more.

Three doses or four doses, depending on the brand, of a Hib vaccine are recommended for children by doctors as the best way to protect against Hib disease.

When should my child get a Hib shot?

One dose at each of the following ages:

• 2 months
• 4 months
• 6 months for some brands
• 12 – 15 months

Why should my child get a Hib shot?

• Protects your child from Hib disease, which can cause lifelong disability and be deadly.
• Protects your child from the most common type of Hib disease, meningitis (an infection of the lining of the brain and spinal cord).
• Keeps your child from missing school or child care, and you from missing work.

Hib shots are safe.

Hib shots are safe and effective at preventing Hib disease. Vaccines, like any medicine, can have side effects. These are usually mild and go away on their own.

What are the side effects?

Most children don’t have any side effects from the shot. The side effects that do occur are usually mild, and may include:

• Redness, swelling, warmth, or pain where the shot was given
• Fever

What is Hib disease?

Hib disease is a serious illness caused by bacteria called Haemophilus influenzae type b (Hib). Babies and children younger than 5 years old are most at risk for Hib disease. It can cause lifelong disability and be deadly.

What are the symptoms of Hib disease?

There are many types of Hib disease. Symptom depend on the part of the body it affects.

The most common type of Hib disease is meningitis. It causes:

• Fever
• Headache or stiff neck
• Nausea with or without vomiting
• Eyes being more sensitive to light
• Confusion
• Poor eating and drinking, low alertness, or irritability (in babies)

Hib disease can also cause:

• Pneumonia (lung infection)
• Throat swelling that makes it hard to breathe
• Infections of the blood, joints, bones, and covering of the heart

Is it serious?

Hib disease is very serious. Most children with Hib disease need care in the hospital. Even with treatment, about 1 in 20 children with Hib meningitis dies. As many as 1 in 5 children who survives Hib meningitis will have brain damage or become deaf.

Haemophilus influenzae type b (Hib) can cause serious illness and death in babies and children younger than 5 years old. CDC recommends Hib vaccination for all children younger than 5 years old in the United States.

Who Should Get a Hib Vaccine?

CDC recommends Hib vaccination for all children younger than 5 years old. Older children and adults usually do not need a Hib vaccine, unless they have certain medical conditions.

Talk to your or your child’s doctor if you have questions about Hib vaccines.

Young Children

Children younger than 5 years old need multiple shots of a Hib vaccine. CDC recommends shots at the following ages:

• 2 months
• 4 months
• 6 months (if needed; depends on brand)
• 12 through 15 months

Older Children and Adults

Older children and adults usually do not need a Hib vaccine. CDC recommends Hib vaccination for two groups of older children and adults:

• People with certain medical conditions who are unvaccinated
• People who receive a bone marrow transplant

Who Should Not Get It?

Because of age or health conditions, some people should not get certain vaccines or should wait before getting them. Read the guidelines below and ask your or your child’s doctor for more information.

Babies younger than 6 weeks old should not get a Hib vaccine. In addition, tell the person who is giving you or your child a Hib vaccine if:

You or your child have had a life-threatening allergic reaction or have a severe allergy.

• Anyone who had a life-threatening allergic reaction after a previous shot of a Hib vaccine should not get another shot.
• Anyone with a severe allergy to any part of a Hib vaccine should not get this vaccine. Your or your child’s doctor can tell you about the vaccine’s ingredients.

You or your child are not feeling well.

• People who have a mild illness, such as a cold, can probably get the vaccine. People who have a more serious illness should probably wait until they recover. Your or your child’s doctor can advise you.

What Types of Hib Vaccine Are There?

The Food and Drug Administration licensed 5 Hib vaccines for use in the United States. Three of the vaccines protect against Hib disease only, while 2 vaccines include protection against other diseases. Your child will get multiple shots; the number depends on the brand given. Doctors can give the first shot as early as 6 weeks, if needed. Doctors can give any of the Hib-only vaccines to older children and adults that need Hib vaccination.

Hib-only Vaccines

• PedvaxHIB: Doctors give three shots to children who are 2 through 15 months old.
• ActHIB: Doctors give four shots to children who are 2 through 15 months old.
• Hiberix: Doctors give four shots to children who are 2 through 15 months old.

A combination vaccine contains two or more vaccines in a single shot in order to decrease the number of shots given.

Combination Vaccines

• Pentacel: Doctors give four shots to children who are 2 through 18 months old. This vaccine protects against Hib disease, diphtheria, tetanus, pertussis (whooping cough), and polio.
• Vaxelis: Doctors give three shots to children who are 6 weeks through less than 1 year old. This vaccine protects against Hib disease, diphtheria, tetanus, pertussis (whooping cough), polio, and hepatitis B.

How Well Do Hib Vaccines Work?

Vaccines that help protect against Hib disease work well, but cannot prevent all cases.

Studies show Hib vaccination protects

• Nearly all (between 93 and 100 in 100) children from Hib disease

Protection decreases over time. Children need a shot between 12 and 15 months old to maintain high levels of protection during early childhood.

What Are the Possible Side Effects?

Most people who get a Hib vaccine do not have any problems with it. With any medicine, including vaccines, there is a chance of side effects. These are usually mild and go away on their own within a few days, but serious reactions are possible.

Mild Problems

Mild problems following Hib vaccination are uncommon. If they occur, they usually begin soon after you or your child receive the shot. They can last up to 2 or 3 days, and include:

• Reactions where the doctor gave the shot
  • Redness
  • Warmth
  • Swelling
• Fever

Problems that Could Happen after Getting Any Injected Vaccine

• People sometimes faint after a medical procedure, including vaccination. Sitting or lying down for about 15 minutes can help prevent fainting, and injuries caused by a fall. Tell your doctor if you or your child:
  • Feels dizzy
  • Has vision changes
  • Has ringing in the ears
• Some people get severe pain in the shoulder and have difficulty moving the arm where the doctor gave the shot. This happens very rarely.
• Any medicine can cause a severe allergic reaction. Such reactions from a vaccine are very rare, estimated at about 1 in a million doses. These types of reactions would happen within a few minutes to a few hours after the vaccination.
• As with any medicine, there is a very remote chance of a vaccine causing a serious injury or death.

Where Can I Find Hib Vaccine?

Your doctor is usually the best place to receive recommended vaccines for you or your child.

Hib vaccine is part of the routine childhood immunization schedule. Therefore, the vaccine is regularly available for children at:

• Pediatric offices
• Family practice offices
• Community health clinics
• Public health departments

If your doctor does not have the Hib vaccine for adults, ask for a referral.

Hib vaccine may also be available for adults at:

• Pharmacies
• Workplaces
• Community health clinics
• Health departments
• Other community locations such as schools and religious centers

Federally funded health centers can also provide services if you don’t have a regular source of health care. Locate one near you. You can also contact your state health department to learn more about where to get vaccines in your community.

When receiving any vaccine, ask the provider to record the vaccine in the state or local registry, if available. This helps healthcare professionals at future encounters know what vaccines you or your child has already received.