Pneumococcal Carriage in Children under Five Years in Uganda-Will Present Pneumococcal Conjugate Vaccines Be Appropriate?

Abstract

Background: Pneumonia is the major cause of death in children globally, with more than 900,000 deaths annually in children under five years of age. Streptococcus pneumoniae causes most deaths, most often in the form of community acquired pneumonia. Pneumococcal conjugate vaccines (PCVs) are currently being implemented in many low-income countries. PCVs decrease vaccine-type pneumococcal carriage, a prerequisite for invasive pneumococcal disease, and thereby affects pneumococcal disease and transmission. In Uganda, PCV was launched in 2014, but baseline data is lacking for pneumococcal serotypes in carriage.

Objectives: To study pneumococcal nasopharyngeal carriage and serotype distribution in children under 5 years of age prior to PCV introduction in Uganda.

Methods: Three cross-sectional pneumococcal carriage surveys were conducted in 2008, 2009 and 2011, comprising respectively 150, 587 and 1024 randomly selected children aged less than five years from the Iganga/Mayuge Health and Demographic Surveillance Site. The caretakers were interviewed about illness history of the child and 1723 nasopharyngeal specimens were collected. From these, 927 isolates of S. pneumoniae were serotyped.

Results: Overall, the carriage rate of S. pneumoniae was 56% (957/1723). Pneumococcal carriage was associated with illness on the day of the interview (OR = 1.50, p = 0.04). The most common pneumococcal serotypes were in descending order 19F (16%), 23F (9%), 6A (8%), 29 (7%) and 6B (7%). One percent of the strains were non-typeable. The potential serotype coverage rate for PCV10 was 42% and 54% for PCV13.

Conclusion: About half of circulating pneumococcal serotypes in carriage in the Ugandan under-five population studied was covered by available PCVs.

Fig 1. Map of the Iganga/Mayuge Health and Demographic surveillance site.

Fig 2. Pneumococcal carriage rate (%) by age group for children <5 years from Uganda, in 2008, 2009, 2011 combined (N = 957/1723)*.

*Age group 0–5 months n = 8, 6–11 months n = 75, 12–23 months n = 194, 24–25 months n = 243, 36–47 months n = 201, 48–59 months n = 230, ages 0–59 months n = 957.

Fig 3. Proportion (%) of pneumococcal carriage serotypes from children <5 years in Uganda in 2008 (n = 86), 2009 (n = 295) and 2011 (n = 546).

Fig 4. Proportion of pneumococcal carriage serotypes covered by pneumococcal conjugate vaccines from children <5 years in Uganda, 2008, 2009 and 2011 (n = 927)*,**, ***.

*The PCV13 bars includes the PCV10 bar + the three extra serotypes (3, 6A and 19A). **NVT is non-vaccine types. ***NT is non-typable