Haemophilus Influenzae bacteria (Hib) was a leading cause in the pre-vaccine era of bacterial meningitis and other invasive bacterial disease among children under 5 years of age, with two-thirds of infections coming in children under 18 months of age. According to the CDC: “Hib disease is not common beyond 5 years of age. Passive protection of some infants is provided by transplacentally acquired maternal IgG antibodies and breastfeeding during the first 6 months of life. In the prevaccine era peak attack rates occurred at 6–7 months of age, declining thereafter. The presumed reason for this age distribution is the acquisition of immunity to Hib with increasing age” (see CDC – Hib). Hib is a serious disease with risk of permanent injury or death (see Disease Risk – Hib). Hib is very uncommon now due to widespread vaccination since the late 1980’s.
Regarding vaccine-injury risks, vaccinating with Hib at 2, 4, and 6 months is associated with an 18% increased risk of asthma. Some Hib vaccines contain aluminum adjuvant, a known neurotoxin (see Does Aluminum cause vaccine-injury?). A parent can request an aluminum-free Hib vaccine such as ACTHib or Hiberix, but Japan recently suspended the use of ACTHib following the deaths of four children. Hib has not been studied for autism rates in children who received vs didn’t receive the Hib vaccine. Although association does not prove causation, the 1988 introduction of the Hib conjugate vaccine in the USA very closely matches the beginning of the autism epidemic (see the Autism Prevalence line chart which demonstrates that Hib was introduced in 1988, the same year that a recent EPA study indicates the autism epidemic began).
A parent considering the Hib vaccine might consider the risks of Hib disease (see Disease Risk – Hib), taking into account that the risk peaks at 6-7 months of age, and weigh this against the demonstrated vaccine-injury risk of asthma and the potential vaccine-injury risk of autism (unknown since the studies have not been performed).