Severe-ApCAP presented at a significant rate in Vietnamese children. More than 50% of severe-ApCAP
cases were associated with pure atypical pathogen infection. M. pneumoniae appeared most frequently. The highest
rate of severe-ApCAP was in children younger than two years. Younger age and co-infection with typical bacteria
or viruses were the most significant risk factors, while respiratory/cardiac system malformation and neonatal
pneumonia were additional potential risk factors, associated with severe-ApCAP in Vietnamese children.