Childhood deaths from two leading bacterial causes of pneumonia and meningitis, pneumococcus and Hib, declined sharply during the period 2000 to 2015, especially as vaccines against these pathogens were introduced in high-burden countries, according to new estimates from a team led by scientists at Johns Hopkins Bloomberg School of Public Health.

Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae (pneumococcus) are bacteria that can cause meningitis, pneumonia, sepsis and other serious complications, especially in children. They have been major causes of child mortality in developing countries. Estimates for the year 2000 showed about 2.1 million severe infections and 299,000 child deaths from Hib, and 6.6 million severe infections and 600,000 child deaths from pneumococcus — not including cases of opportunistic infection in children with HIV.

Their primary findings were that both Hib and pneumococcus caused far fewer cases of severe disease and death in children ages one to 59 months in 2015 compared to 2000. For Hib in 2015, there were approximately 29,500 child deaths, and for pneumococcus an estimated 294,000 child deaths. These figures suggest declines of 90 percent and 51 percent, respectively, from the estimated deaths in the year 2000.

The researchers estimated that Hib and pneumococcal deaths among children with HIV/AIDS also declined sharply — 75 percent — from about 95,000 in 2000 to about 23,000 in 2015.

The sharp declines in child mortality from Hib and pneumococcus were due not just to the introduction of vaccines but also to general factors that have reduced pneumonia and meningitis deaths from all causes, such as better hygiene and access to health care. "In 2015 compared to 2000 fewer children died from all causes, not just Hib and pneumococcus," Wahl notes.