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Table 2 Acquisition and clearance of Streptococcus pneumoniae carriage in a day-care centre in Portugal, 1998–1999

From: Comparative analysis of Streptococcus pneumoniaetransmission in Portuguese and Finnish day-care centres

  Clearance Acquisition in non-carriers Acquisition in carriers
Target serotype Exposure1 Events Person-time2 Events Person-time3 Events Person-time4
19F Yes 19 58 17 96 5 85
No 2 2 3 19 0 20
23F Yes 10 23 10 47 2 54
No 1 3 2 68 1 85
6B Yes 2 13 5 44 5 61
No 3 7 2 71 3 84
14 Yes 2 10 3 17 6 27
No 0 0 2 98 4 128
10A Yes 2 11 1 27 1 44
No 2 2 4 88 5 108
19A Yes 3 7 1 33 0 37
No 2 4 2 82 2 117
NT Yes 1 5 1 44 3 52
No 1 6 1 71 3 102
16F Yes 0 0 0 18 0 21
No 1 2 2 97 3 142
18F Yes 1 1 1 4 0 7
No 0 0 1 111 2 157
11A Yes 0 0 0 13 1 25
No 2 3 0 102 0 137
23B Yes 0 0 0 6 0 4
No 1 1 1 109 0 160
9V Yes 0 2 0 21 1 34
No 0 4 1 94 0 125
15A Yes 0 0 0 4 0 7
No 0 1 1 111 0 157
8 Yes 0 0 0 0 0 0
No 0 0 0 115 1 165
Total: Yes 40 130 39 374 24 458
No 15 35 22 1236 24 1687
55 165 78 1610 48 2145
  1. The crude estimates of the model parameters are (cf. Appendix): the transmission rate β ^ = 39 κ ^ × 374 / 60.18 = 0.54 (per month); the community acquisition rate per serotype (in non-carrying children) κ ^ = 22 / 1236 = 0.018 (per month); the clearance rate of carriage μ ^ = 55 / 165 = 0.33 (per month); the competition parameter ϕ ^ = 24 / 1687 / 22 / 1236 = 0.80 . For parameter β, the denominator (60.18) is not directly readable from the data as presented in the table. Only samples available from two consecutive visits were considered, accounting for 67% of the scheduled pairs of consecutive visits. The three rooms were analysed as six rooms, separated by the summer break.
  2. 1 Exposure is here defined as the presence of at least one carrier of the target serotype in the other attendees in the room.
  3. 2 Person-time here is the total time, in months, spent carrying pneumococcus overall (total row) or a specific serotype (serotype rows) stratified by the presence or absence of other carriers of the specific serotype.
  4. 3 Person-time here is the total time, in months, spent as a non-carrier, stratified by exposure to the specific serotype. For the total row, the time is a sum of serotype-specific person-times.
  5. 4 As in 2 but for children carrying pneumococcus.