Volume 29, Number 2—February 2023
Research
Incidence and Transmission Dynamics of Bordetella pertussis Infection in Rural and Urban Communities, South Africa, 2016‒2018
Table 2
Incidence rate and factors associated with Bordetella pertussis incidence for 1,684 participants in the PHIRST study of respiratory infections, South Africa, 2016–2018*
Characteristic | B. pertussis incidence (95% CI) | Univariate analysis |
Multivariable analysis |
|||
---|---|---|---|---|---|---|
Incidence rate ratio (95% CI) | p value | Adjusted incidence rate ratio (95% CI) | p value | |||
Overall |
0.2 (0.17–0.25) |
NA |
NA |
NA |
NA |
|
Year | ||||||
2016 | 0.25 (0.17–0.35) | Referent | NA | NA | ||
2017 | 0.13 (0.09–0.19) | 0.53 (0.17–1.63) | 0.27 | NA | NA | |
2018 |
0.26 (0.20–0.33) |
1.04 (0.44–2.49) |
0.92 |
NA |
NA |
|
Site | ||||||
Rural | 0.17 (0.13–0.22) | Referent | NA | NA | ||
Urban |
0.24 (0.19–0.31) |
1.5 (0.77–2.96) |
0.23 |
NA |
NA |
|
Sex | ||||||
M | 0.23 (0.17–0.30) | Referent | NA | NA | ||
F |
0.19 (0.15–0.24) |
0.83 (0.58–1.19) |
0.31 |
NA |
NA |
|
Age group, y | ||||||
<5 | 0.21 (0.14–0.33) | 1.41 (0.69–2.90) | 0.37 | 1.62 (0.56–4.65) | 0.37 | |
5–14 | 0.27 (0.20–0.35) | 1.76 (0.96–3.21) | 0.09 | 1.73 (0.91‒3.31) | 0.09 | |
15–44 | 0.17 (0.12–0.24) | 1.12 (0.62–2.04) | 0.78 | 1.09 (0.59–2.00) | 0.78 | |
>45 |
0.15 (0.09–0.25) |
Referent |
Referent |
|||
HIV status | ||||||
Uninfected | 0.22 (0.18–0.27) | Referent | NA | NA | ||
Infected |
0.14 (0.08–0.25) |
0.64 (0.36–1.11) |
0.11 |
NA |
NA |
|
Nutritional status† | ||||||
Underweight | 0·20 (0.10–0.38) | 0.68 (0.28–1.66) | 0.39 | NA | NA | |
Normal | 0.23 (0.18–0.28) | Referent | NA | NA | ||
Overweight/obese |
0.30 (0.21–0.43) |
0.76 (0.52–1.13) |
0.18 |
NA |
NA |
|
Underlying illness‡ | ||||||
No | 0.20 (0.17–0.24) | Referent | NA | NA | ||
Yes |
0.36 (0.16–0.80) |
1.78 (0.68–4.70) |
0.24 |
NA |
NA |
|
Pertussis vaccination§ | ||||||
Incomplete | 0.91 (0.23–3.64) | 4.89 (1.47–16.02) | 0.01 | 4.48 (1.38–14.59) | 0.01 | |
Fully vaccinated | 0.19 (0.11–0.32) | Referent | Referent | |||
Unknown |
0.20 (0.17–0.25) |
1.08 (0.61–1.91) |
0.78 |
1.32 (0.42–4.13) |
0.64 |
|
Crowding¶ | ||||||
No | 0.15 (0.11–0.21) | Referent | Referent | |||
Yes | 0.25 (0.20–0.31) | 1.63 (0.86–3.08) | 0.13 | 1.53 (0.78–2.97) | 0.21 |
*Bold indicates statistical significance. Variables adjusted for in final model were age group, pertussis vaccination, and crowding. NA, not applicable; PHIRST, Prospective Household cohort study of Influenza, Respiratory Syncytial virus, and other respiratory pathogens community burden and Transmission dynamics in South Africa. †Nutritional status is based on a person’s body mass index (BMI). We defined BMI categories as follows: underweight, age <18 y weight for age or BMI <‒2 SDs of World Health Organization (WHO) Child Growth Standards; age >18 y BMI <18.5 kg/m2; overweight, age <18 y BMI >+1 and ≤+2 SD of the WHO growth standards, age ≥18 y BMI ≥25 and <30 kg/m2; obese, age <18 y BMI >+2 SD of WHO growth standards, age ≥18 y BMI >30 kg/m2. ‡Defined as self-reported history of asthma, lung disease, heart disease, stroke, spinal cord injury, epilepsy, organ transplant, immunosuppressive therapy, organ transplantation, cancer, liver disease, renal disease, or diabetes. §Collected only for children <5 y of age· Vaccine status calculate based on number of doses of vaccine received by age. ¶More than 2 persons in a household sleeping in the same room.