. 2019 Oct 4;7(12):1068–1083. doi: 10.1016/S2213-2600(19)30249-8

Table 1.

Established risk factors for pneumonia in children

	Prevalence	Mechanisms
Not exclusively breastfeeding (children aged 0–5 months)	61% of children aged 0–5 months globally³	Suboptimal maternal antibody transmission; suboptimal nutrition
Underweight (weight-for-age <–2 SD)	20·2% of children <5 years in low-income and middle-income countries.⁴	Poorly characterised immune deficiency
Stunting (height-for-age <–2 SD)	32·0% of children <5 years in low-income and middle-income countries⁴	Poorly characterised immune deficiency
Severe wasting (weight-for-length <–3 SD)	3·5% of children <5 years in low-income and middle-income countries⁴	Poorly characterised immune deficiency
Zinc deficiency	7·5–30% globally, all ages⁵	Impairs various immune functions, including the integrity of respiratory cells during lung inflammation or injury
Exposure to household air pollution	Approximately 40% worldwide⁶	Impairment of respiratory tract defence mechanisms, local oxidative stress, and inflammation
Non-vaccination	Haemophilus influenzae type b (30%); measles (2 doses) [36%]; Pneumococcus (3 doses of a conjugate vaccine) pertussis (as DTP3)[14%].⁷	Disease-specific immunity

SD= standard deviation. DTP3= Diphtheria-tetanus-pertussis vaccine.