HAEMOPHILUS INFLUENZA TYPE B (HIB)

Haemophilus influenza type b was first isolated in 1892 from victims in an influenza epidemic. This bacteria lives in the human respiratory tract and can be recovered from the nasal and throat passages of up to 90 percent of all healthy individuals. American children aged 6 to 48 months are highly susceptible to developing Hib infection, especially if they are immune compromised or live in crowded, substandard living conditions. Hib disease is spread through sneezing, coughing or inhaling respiratory tract secretions of an infected person. Hib infections occur most often during the late winter and spring.

Historically, Hib disease has been rare in newborns and adults, although the incidence of Hib disease increased fourfold between the years 1946 and 1986 and more adults have became vulnerable. The reason for the sudden increase in the incidence and severity of Hib disease in this century is unknown. However, some scientists believe that excessive use of antibiotics may have caused the organism to change and become more virulent. Common antibiotics, such as ampicillin, which once were used to help people recover from the disease, are no longer effective treatments for Hib disease because the bacteria have become resistant to it.

Hib was the most common cause of bacterial meningitis affecting children between 6 months and 4 years of age prior to the use of the vaccine. It is not known how long the incubation period lasts. Symptoms can begin with cough, fever, chills, lack of appetite, extreme sleepiness, vomiting and, as older children and adults can testify, a severe headache. A stiff neck or back can be a warning sign. More serious signs are mental confusion, convulsions, shock and coma. In some extremely severe cases of Hib disease, a child can die within a few hours. Some cases of otitis media, sinusitis and bronchitis are also caused by Hib organisms. A spinal tap (lumbar puncture) to examine the cerebrospinal fluid (CSF), blood and urine lab tests can confirm Hib disease.

Without immediate and adequate medical treatment, Hib disease has a significant death rate (5 to 10 percent) and a high rate of seizures and other neurological complications (30 percent). Other complications include pneumonia and heart involvement with long term damage including hearing loss and neurological dysfunction. Antibiotic therapy using powerful antibiotics is only one part of the treatment, which may include respiratory and oxygen therapy, blood transfusions, fluid replacement, tracheostomy, and anticonvulsant therapy.

When a Hib disease case is confirmed, often both unvaccinated AND vaccinated children within the same family or classroom are given "prophylactic" antibiotic therapy in an attempt to prevent infection. Recovery from Hib disease sometimes confers permanent immunity but sometimes it does not and the individual, especially if he or she is immune compromised, can come down with another Hib infection.

In 1984, there were 20,000 cases of Hib disease estimated to have occurred in the U.S. that year, the highest number that are thought to have occurred in one year. In 1994, there were 1,174 cases of Hib disease reported, with 329 cases occurring in children under five years of age and 463 occurring in adults over 60 years old. Today Hib has become a rare cause of invasive disease, including meningitis, in children under age five in the U.S. In 2002 there were only 34 confirmed cases of Hib disease in children under age 5. In 1992, 16 deaths were reported to be due to complications from Hib infection and in 2000 only 6 deaths were reported.

HAEMOPHILUS INFLUENZA TYPE B VACCINE (HIB)

Reported common reactions to Hib vaccine include fever and pain and swelling at injection site. Rash, hives, irritability, restless sleep, prolonged crying; diarrhea, vomiting, loss of appetite, convulsions, collapse/shock, and Guillain-Barre syndrome have also been reported. Some of the studies used to evaluate the reactivity of Hib vaccine were complicated by the fact that Hib vaccine was given simultaneously with DPT an OPV vaccine. When a reaction occurred, it was difficult to determine which vaccines were responsible for the reaction.

In 1994, the Institute of Medicine concluded that there is compelling scientific evidence that vaccination with earlier versions of the Hib vaccine resulted in early onset of Hib disease in children over 18 months of age. Apparently, the early Hib vaccines caused children, who had been recently vaccinated, to be immune suppressed for at least 7 days after vaccination.

The conjugate Hib vaccines now being used are thought to be more quickly effective, leaving children less vulnerable to Hib disease shortly after vaccination. However, the IOM report stated that "Because immunization with Hib vaccines may lead to a transient decrease in protective antibody levels, unimmunized children at increased risk of colonization (household or day-care contact with individuals with recent cases of Hib infection) may require special [protective] measures." One Hib vaccine manufacturer states, "There have been rare reports to the Vaccine Adverse Events Reporting System (VAERS) of Hib disease following full primary immunization."

Because either no studies or too few studies have ever been conducted to investigate Hib vaccine reactions, the IOM could not make a determination about whether Hib vaccine causes transverse myelitis, Guillain-Barre syndrome, thrombocytopenia, anaphylaxis and sudden infant death syndrome.

A manufacturer of HIB vaccine states in the product insert that the vaccine "has not been evaluated for its carcinogenic, mutagenic potential or impairment of fertility" and "it is also not known whether [the vaccine] can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity."

In 1995, out of 74 Hib disease cases where age and vaccination status were known, 41 or 55 percent had received at least one Hib shot; 22 were appropriately vaccinated for their age; and 18 had completed the primary series.