Table 2.

Individual contribution of the two mechanisms toward serotype replacement in IPD

	Israel	South Africa	USA
Mechanism 1*
Number of non-VT GPSCs	36	66	24
Non-VT IPD cases caused by non-VT GPSCs in the pre-PCV period	49/56 (88%)	111/122 (91%)	7/11 (64%)
Non-VT IPD cases caused by non-VT GPSCs in the PCV13 period†	153/195 (78%)	168/209 (80%)	63/106 (59%)
Incidence of non-VT IPD caused by non-VT GPSCs in the pre-PCV period, per 100 000 children	8·2	4·5	6·8
Incidence of non-VT IPD caused by non-VT GPSCs in the PCV13 period, per 100 000 children	15·8	4·7	6·0
IRR (95% CI, p value)‡	1·9 (1·4–2·6, p<0·0001)	1·1 (0·7–1·6, p=0·78)	0·9 (0·7–1·2, p=0·40)
Mechanism 2§
Number of VT GPSCs	47	53	29
Non-VT IPD cases caused by VT GPSCs in the pre-PCV period	7/56 (12%)	11/122 (9%)	4/11 (36%)
Non-VT IPD cases caused by VT GPSCs in the PCV13 period†	42/195 (22%)	41/209 (20%)	43/106 (41%)
Incidence of non-VT IPD caused by VT GPSCs in the pre-PCV period, per 100 000 children	1·3	0·4	2·6
Incidence of non-VT IPD caused by VT GPSCs in the PCV13 period, per 100 000 children	4·2	1·1	4·1
IRR (95% CI, p value)‡	3·4 (1·8–6·3; p<0·0001)	2·5 (1·6–3·9; p<0·0001)	1·6 (1·0–2·4; p=0·12)

VT=vaccine type. GPSC=Global Pneumococcal Sequence Cluster. IPD=invasive pneumococcal disease. PCV=pneumococcal conjugate vaccine. IRR=incidence rate ratio.

^*Increase in disease caused by non-VT GPSCs (ie, those expressing >50% non-vaccine serotypes in the pre-PCV13 period).

^†The PCV13 period represented 4 years (2011–14) in Israel, 2 years (2013–14) in South Africa, and 1 year (2012) in the USA.

^‡IRRs were calculated with the estimated incidence of non-VT IPD caused by VT or non-VT GPSCs per year for the pre-PCV and PCV13 periods.

^§Increase in non-VT component within VT GPSCs (ie, those expressing ≥50% vaccine serotype in the pre-PCV period).