The prevalence and influencing factors of the oropharyngeal carriage of Haemophilus influenzae in healthy children in a high-altitude area of China: A cross-sectional study.

Haemophilus influenzae is a common commensal organism of the human upper respiratory tract and an important cause of human disease. No data on H influenzae carriage rate has been carried out on the Qinghai-Tibet Plateau of China. This study aims to present the H influenzae carriage rate and influencing factors of H influenzae in healthy children <15 years of age in Qinghai Province, an area located on the Qinghai-Tibet Plateau in China. Oropharyngeal swabs for the detection of H influenzae DNA were collected between September and October 2019. Taqman real-time polymerase chain reaction was used to detect the nucleic acids from the oropharyngeal swabs. Self-designed questionnaires were used to investigate the related information among this group of children. A number of 284 children were enrolled in this study. The carriage rate of H influenzae was 44.7%. The carriage rate in cities was 47.5%, in rural areas was 21.9%, and in pastoral areas was 52.8%. The carriage rate was found to be higher among children of minority ethnic groups than those of Han ethnicity (55.6% vs 38.1%). H influenzae carriage rate was influenced by tobacco smoke exposure (adjusted odds ratio [aOR] = 2.31, 95% CI [confidence interval]: 1.14-4.70), having siblings <5 years of age (aOR = 2.36, 95% CI: 1.21-4.59), respiratory infections during the last 30 days (aOR = 2.37, 95% CI: 1.11-5.06), and parent/guardian education level (aOR = 0.08, 95% CI: 0.02-0.27). H influenzae was highly prevalent in healthy children in Qinghai Province, especially among children of minority ethnicities and those living in pastoral areas. Tobacco smoke exposure, having siblings <5 years of age, and respiratory infections during the last 30 days were risk factors for H influenzae carriage. Parents or guardians having education levels of college or higher was a protective factor for H influenzae carriage. It is of critical importance that the government take effective measures to reduce the carriage rate and the occurrence of H influenzae related diseases in susceptible populations.

Duration of maternally derived antibody against measles: a seroepidemiological study of infants aged under 8 months in Qinghai, China.

To estimate the sero-prevalence of protective maternal measles antibodies among young infants and examine patterns of waning immunity in one of the poorest provinces in China, infants aged under 8 months and their mothers were randomly selected by multi-stage probabilistic sampling and blood samples were collected. Measles-specific IgG antibodies were measured in all serum samples by enzyme-linked immunosorbent assay. We determined measles-specific antibody titres for 477 pairs of infants and their mothers. After excluding 44 sub-clinical measles infection in infants, the measles antibody titres were ≧1:200, ≧1:800, and ≧1:3200 in 79.2%, 46.9%, and 17.8% of the 433 infants, respectively. The proportion of infants with titre ≧1:800 declined with age from 90.2% in newborns to 45.5% and 14.9% in the fourth and eighth month, respectively. Among the 433 mothers, measles antibody titres were ≧1:800 in 94.0%. Multivariate regression analysis showed that residence, mother's antibody levels and infant's age were significantly associated with infants' having a measles antibody titre ≧1:800. The relatively rapid decay of protective antibody in infants suggests that an earlier administration of the first dose of measles vaccination should be considered in China and a high quality interventional study is needed to decide the optimal schedule of measles immunization.