Five years after the Haemophilus influenzae type b (or Hib) jab was introduced as routine for US children, researchers are finding that, while the incidence of bacterial meningitis is declining among children, the disease is becoming more common in adults.

The decline in the number of childhood cases actually supercedes the advent of the routine Hib jab. The average age for meningitis patients has been rising steadily; from 15 months in 1986 to 25 years in 1995.

This raises several questions, such as whether it really is the vaccine which has caused the decline among children or other as yet unevaluated factors. Also, as meningitis becomes an adult disease, what is the best way to treat it? In the adult age group, the bacteria most often responsible for meningitis is the S pneumoniae already highly resistant to antibiotic therapy. Medicine's answer, according to the authors of the recent survey of four American states, is to develop effective vaccines for adults as well (N Eng J Med, 1997; 337: 970-6).

Because the Hib jab is relatively new, we do not yet know the long-term consequences of its widespread use. Nor has another crucial factor been properly addressed through medical research.

A number of the available Hib vaccines have been shown to have a number of problems with efficacy. Some studies have shown that the jab may increase the risk of contracting the disease by lowering natural antibody response (see WDDTY's Vaccination Bible).