The number of deaths attributable to pneumococcal disease and Haemophilus influenzae type b decreased significantly on a global scale between 2000 and 2015, with approximate decreases of 90% in Haemophilus influenzae type b–related deaths and 51% in pneumococcal disease-related deaths reported.
According to the researchers, vaccination using pneumococcal conjugate vaccines prevented an estimated 250,000 deaths, and vaccination against Haemophilus influenzae type b (Hib) prevented approximately 1.2 million total deaths in HIV-uninfected children.
“There are multiple factors that have contributed to the decline in pneumococcal- and Hib-related deaths,” Brian Wahl, PhD, assistant scientist at the International Vaccine Access Center at the Bloomberg School’s department of international health, told Infectious Diseases in Children. “Fewer children are dying overall in many resource-poor settings due to improved access to effective treatment. Further, we estimate in this study that vaccines have also contributed to the reduction in deaths from these two human pathogens.”
Wahl and colleagues calculated estimates of the burden associated with pneumococcal disease and Hib on a regional, national and global scale by accessing WHO and Maternal Child Health Epidemiology country-specific estimates of pneumonia and meningitis mortality. Additionally, these estimates also included data on pneumonia morbidity. All morbidities and mortalities occurred between 2000 and 2015.
Between 2000 and 2015, approximately 1.4 million pediatric deaths were prevented globally. Significant decreases in both pneumococcal and Hib-related deaths were observed during this time.
Once estimates were collected, pneumococcal and Hib cause-specific proportions were used to estimate the number and proportion of deaths and cases attributable to specific pathogens, which were taken from four Hib and six pneumococcal conjugate vaccine efficacy and effectiveness study values. Illnesses related to pneumococcal and Hib syndromes, excluding pneumonia and meningitis, were approximated using the proportion of pathogen-specific nonpneumonia, nonmeningitis cases to pathogen-specific cases of meningitis.
The researchers noted that HIV infection prevalence, availability of care and immunization practices were considered in the estimates.
In 2015, approximately 294,000 pneumococcal deaths (uncertainty range, 192,000-366,000) and 29,500 Hib deaths (18,400-40,700) were experienced in HIV-negative children aged between 1 and 59 months. Furthermore, Wahl and colleagues estimate that 23,300 deaths were attributable to pneumococcal deaths (15,300-28,700) and less than 1,000 deaths were related to Hib in children with HIV infection.
According to the researchers, these estimates imply that pneumococcal deaths dropped 51% (7-74) between 2000 and 2015. A larger decrease was observed in Hib deaths, with an approximate 90% reduction (78-96) during this time. Those who experienced mortality frequently presented with pneumonia (pneumococcus: 81%; Hib: 76%).
About half of all pneumococcal-related mortalities in 2015 were reported in countries within Africa and Asia, including India (68,700 deaths [44,600-86,100]), Nigeria (49,000 deaths [32,400-59,000]), the Democratic Republic of Congo (14,500 deaths [9,300-18,700]) and Pakistan (14,400 deaths [9,700–17,000]). In 2015, Hib deaths were most commonly reported in India (15,600 deaths [9,800-21,500]), Nigeria (3,600 deaths [2,200-5,100]), China (3,400 deaths [2300-4600]) and South Sudan (1,000 deaths [600-1,400]).
Wahl and colleagues estimate that 3.7 million cases of severe pneumococcal disease (2.7 million-4.3 million) and 340,000 cases of severe Hib (196,000-669,000) occurred globally in 2015.
“Far too many preventable deaths are still occurring due to pneumococcus and Hib,” Wahl said. “A limited number of countries in Africa and Asia account for most of the remaining deaths from these bacteria. Global progress toward further reducing the burden of pneumococcus could be accelerated by improving vaccine coverage in countries that have already started using the vaccines and introducing the vaccines in countries that are not yet using them routinely.”
“Increased access to other interventions that provide children protection from pneumonia, the dominant syndrome associated with each pathogen, should also be scaled up in countries with high disease burdens,” he continued. “These include exclusive breast-feeding for the first 6 months of life, reduced exposure to indoor and outdoor air pollution and improved access to effective care and treatment.” – by Katherine Bortz
Disclosures: Wahl reports grants from the Bill & Melinda Gates Foundation, Gavi, the Vaccine Alliance, and Pfizer. Please see the full study for a list of all other authors’ relevant financial disclosures.