Health Sciences Unit, Faculty of Social Sciences, Tampere University, Finland; Expanded Programme on Immunization, Cameroon; National Institute for Health and Welfare (THL), Finland.
Institute of Biomedicine, Research Center for Cancer, Infections and Immunity, University of Turku, Finland.
Int J Infect Dis. 2020 Sep;98:113-120. doi: 10.1016/j.ijid.2020.06.048. Epub 2020 Jun 17.
Streptococcus pneumoniae remains a major contributor to childhood infections and deaths globally. In Cameroon, the 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in July 2011, using a 3-dose Expanded programme on immunization (EPI) schedule administered to infants at 6, 10 and 14 weeks of age. To evaluate PCV13 effects, we assessed pneumococcal nasopharyngeal colonization and serotype distribution among Cameroonian children after PCV13 introduction.
Nasopharyngeal (NP) swabs were collected from eligible children aged 24-36 months in two cross-sectional surveys conducted from March to July: in 2013 (PCV13-unvaccinated), and in 2015 (PCV13-vaccinated). Using a systematic World Health Organization (WHO) cluster coverage sampling technique in 40 communities, NP swabs collected were processed following WHO recommendations. Standard bacterial culture techniques were used for the isolation of S. pneumoniae from gentamicin-blood agar plates and identification using optochin susceptibility testing. Serotyping was performed using sequential multiplex polymerase chain reaction, supplemented with Quellung test.
Among the PCV13-vaccinated children, overall pneumococcal carriage prevalence was 61.8% (426/689) and PCV13 vaccine-type carriage prevalence was 18.0% (123/689). Eleven out of the 13 vaccine serotypes were detected in the vaccinated children. The most common serotypes were 19F (4.5%, 31/689) and 15B/C (7.3%, 50/689).
In Cameroon, four years after infant vaccination nearly all of the PCV13-serotypes continued to circulate in the population. This suggests that the direct and indirect effects of the vaccination programme have not resulted in expected low levels of vaccine-type transmission. Continuous monitoring is needed to assess the long term effects of the PCV13 on nasopharyngeal carriage and disease.
肺炎链球菌仍然是全球儿童感染和死亡的主要原因。在喀麦隆，13 价肺炎球菌结合疫苗（PCV13）于 2011 年 7 月通过扩大免疫规划（EPI）计划引入，为 6、10 和 14 周龄的婴儿接种 3 剂。为了评估 PCV13 的效果，我们评估了 PCV13 引入后喀麦隆儿童的肺炎球菌鼻咽定植和血清型分布。
在 2013 年（PCV13 未接种）和 2015 年（PCV13 接种）进行的两项横断面调查中，从 24-36 个月龄符合条件的儿童中采集鼻咽（NP）拭子。使用系统的世界卫生组织（WHO）集群覆盖采样技术在 40 个社区中进行采样，按照 WHO 建议处理采集的 NP 拭子。使用标准的细菌培养技术从庆大霉素血琼脂平板上分离肺炎链球菌，并通过奥普林敏感性试验进行鉴定。使用连续多重聚合酶链反应进行血清型分析，并辅以 Quellung 试验。
在 PCV13 接种的儿童中，肺炎球菌总携带率为 61.8%（426/689），PCV13 疫苗型携带率为 18.0%（123/689）。接种儿童中检测到 13 种疫苗血清型中的 11 种。最常见的血清型为 19F（4.5%，31/689）和 15B/C（7.3%，50/689）。
在喀麦隆，婴儿接种疫苗四年后，几乎所有的 PCV13 血清型仍在人群中传播。这表明疫苗接种计划的直接和间接影响并未导致预期的疫苗型传播水平降低。需要持续监测以评估 PCV13 对鼻咽携带和疾病的长期影响。
