Table 2. Predictors through binary logistic regression of Streptococcus pneumoniae carriage^a (n = 2,615 nasopharyngeal samples) and of PCV13-non-PCV10 vaccine serotype carriage^b (n = 1,744) among children attending day care (pooled over study periods), Belgium, 2016–2018.

Number of samples/isolatesc			Univariate regression			Multiple regression
Characteristic	n	%	OR	95% CId		OR		95% CId
Predictors of Sp-carriagea
Study period
2016	760	29.1	REF		REF		REF	REF
2016–2017	902	34.5	0.78		0.62–0.99		0.64	0.47–0.87
2017–2018	953	36.4	0.92		0.73–1.16		0.71	0.52–0.96
Region
Wallonia	922	35.3	REF		REF		REF	REF
Flanders	1,372	52.5	1.29		1.06–1.57		1.09	0.83–1.42
Brussels	321	12.3	1.42		1.04–1.95		1.16	0.81–1.66
Sex
Female	1,304	49.9	REF		REF		REF	REF
Male	1,311	50.1	0.75		0.63–0.91		0.76	0.62–0.93
Common cold symptomse
Yes	942	36.1	REF		REF		REF	REF
No	1,668	63.9	0.65		0.53–0.80		0.64	0.51–0.80
Sa-carriagef
Yes	116	4.4	REF		REF		REF	REF
No	2,499	95.6	1.71		1.14–2.55		1.79	1.13–2.85
Hi-carriageg
Yes	2,402	91.9	REF		REF		REF	REF
No	213	8.1	0.58		0.43–0.79		0.64	0.45–0.90
Mc-carriageg
Yes	2,382	91.1	REF		REF		REF	REF
No	233	8.9	0.26		0.19–0.34		0.31	0.23–0.42
Siblingsh
Yes	1,606	62.4	REF		REF		REF	REF
No	969	37.6	0.72		0.59–0.87		0.73	0.61–0.89
AOM-historyI,j
Yes	682	26.9	REF		REF		REF	REF
No	1,855	73.1	1.36		1.11–1.67		1.14	0.91–1.44
AB-use < 3 monthsk,l
Yes	719	29.3	REF		REF		REF	REF
No	1,739	70.7	1.79		1.47–2.18		1.63	1.30–2.05
Age (months)
6–12	524	20.0	0.81		0.64–1.03		0.94	0.73–1.22
13–24	1,400	53.5	REF		REF		REF	REF
25–30	691	26.4	0.79		0.64–0.99		0.84	0.65–1.07
Sampled during influenza-peak
Yes	1,072	41.0	REF		REF		REF	REF
No	1,543	59.0	1.23		1.02–1.48		1.01	0.77–1.33
Predictors of PCV13-non-PCV10-VT-carriageb
Study period
2016	463	26.5	REF		REF		REF	REF
2016–2017	613	35.1	1.90		0.59–6.11		1.36	0.36–5.07
2017–2018	668	38.3	9.69		3.48–27.00		5.88	1.56–22.19
Vaccination schedulem
PCV13	486	27.9	REF		REF		REF	REF
PCV10	707	40.6	6.85		2.70–17.35		1.79	0.53–6.01
Incomplete	222	12.7	1.77		0.47–6.64		0.92	0.22–3.87
Mix	328	18.8	3.03		1.02–8.93		1.71	0.50–5.82
Sampled during RSV-peak
Yes	601	34.5	REF		REF		REF	REF
No	1143	65.5	0.512		0.313-0.838		0.88	0.52–1.50

AB: antibiotic; AOM: acute otitis media; CI: confidence interval; Hi: Haemophilus influenza; Mc: Moraxella catarrhalis; OR: odds ratio; PCV: pneumococcal conjugate vaccine; PCV13-non-PCV10-VT: vaccine serotypes included in PCV13, but not in PCV10 (serotypes: 3, 6A, 19A); REF: reference group for the regression analysis; RSV: respiratory syncytial virus; Sa: Staphylococcus aureus; Sp: Streptococcus pneumoniae.

^a Knowledge of Sp carriage was through results of culture and PCR combined.

^b Knowledge of PCV13-non-PCV10 vaccine serotype carriage was based on culture or Quellung-reaction results.

^c The number of samples was used for the analyses regarding Sp-carriage predictors; the number of isolates was used for the analyses regarding PCV13-non-PCV10-VT-carriage predictors.

^d Confidence intervals that do not overlap the null value of OR = 1 are indicated in bold.

^e Information on common cold symptoms was not available for five children.

^f Based on culture-results or Quellung-reaction.

^g Based on the combination of culture and PCR-results.

^h Information on siblings was not available for 40 children.

ⁱ Child with a history of AOM.

^j Information on history of AOM was not available for 78 children.

^k Use of antibiotics in the 3 months before sampling.

^l Information on use of antibiotics in the 3 months before sampling was not available for 157 children.

^m Information on vaccination status was missing for one child.

Besides the shown confounders, other variables were assessed, but not significant in univariate analysis: preterm delivery, previous hospitalisation, age-appropriate vaccination, carriage of Streptococcus pyogenes (based on culture-results or Quellung-reaction), parental smoking, breastfeeding.