Dr. John B. Robbins, a pioneer in vaccinology and one of the inventors of the first effective defense against a form of meningitis that once killed more than a thousand infants a day worldwide, died on Nov. 27 at his home in Manhattan. He was 86.

The cause was prostate cancer, his son Robert said.

By some estimates, Dr. Robbins’s vaccine against the illness, called Hib meningitis, has saved seven million lives since it was licensed in 1989.

Pediatricians who worked in the pre-vaccine days remember feeling their hearts sink when they saw Hib bacteria under a microscope in a baby’s spinal fluid. It meant that, even with antibiotics, the child was at risk of permanent brain damage, deafness or death.

Before the vaccine, Hib meningitis killed about 400,000 children a year, according to the World Health Organization.