Table 1.
Characteristics of patients hospitalised with laboratory-confirmed influenza, by influenza vaccination status
|
Children aged 6–24 months |
Adults 18–64 years with pre-existing medical conditions* |
Older adults aged ≥65 years |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Unvaccinated (n=386) | Partially vaccinated* (n=193) | Fully vaccinated* (n=70) | p value | Unvaccinated (n=402) | Vaccinated (n=118) | p value | Unvaccinated (n=969) | Vaccinated (n=609) | p value | |||
| Country | .. | .. | .. | <0·0001 | .. | .. | 0·0543 | .. | .. | <0·0001 | ||
| Argentina | 27 (7·0%) | 24 (12·4%) | 8 (11·4%) | .. | 0 | 0 | .. | 69 (7·1%) | 34 (5·6%) | .. | ||
| Brazil | 58 (15·0%) | 56 (29·0%) | 20 (28·6%) | .. | 21 (5·2%) | 11 (9·3%) | .. | 90 (9·3%) | 104 (17·1%) | .. | ||
| Chile | 146 (37·8%) | 82 (42·5%) | 36 (51·4%) | .. | 357 (88·8%) | 105 (89·0%) | .. | 611 (63·1%) | 440 (72·2%) | .. | ||
| Paraguay | 155 (40·2%) | 31 (16·1%) | 6 (8·6%) | .. | 24 (6·0%) | 2 (1·7%) | .. | 199 (20·5%) | 31 (5·1%) | .. | ||
| Year | .. | .. | .. | 0·10 | .. | .. | 0·55 | .. | .. | 0·0001 | ||
| 2013 | 86 (22·3%) | 58 (30·1%) | 25 (35·7%) | .. | 23 (5·7%) | 9 (7·6%) | .. | 143 (14·8%) | 125 (20·5%) | .. | ||
| 2014 | 43 (11·1%) | 29 (15·0%) | 13 (18·6%) | .. | 45 (11·2%) | 15 (12·7%) | .. | 113 (11·7%) | 102 (16·7%) | .. | ||
| 2015 | 66 (17·1%) | 25 (13·0%) | 8 (11·4%) | .. | 78 (19·4%) | 18 (15·3%) | .. | 174 (18·0%) | 110 (18·1%) | .. | ||
| 2016 | 55 (14·2%) | 25 (13·0%) | 7 (10·0%) | .. | 38 (9·5%) | 18 (15·3%) | .. | 111 (11·5%) | 46 (7·6%) | .. | ||
| 2017 | 29 (7·5%) | 11 (5·7%) | 2 (2·9%) | .. | 59 (14·7%) | 17 (14·4%) | .. | 194 (20·0%) | 88 (14·4%) | .. | ||
| 2018 | 39 (10·1%) | 17 (8·8%) | 9 (12·9%) | .. | 58 (14·4%) | 15 (12·7%) | .. | 135 (13·9%) | 76 (12·5%) | .. | ||
| 2019 | 68 (17·6%) | 28 (14·5%) | 6 (8·6%) | .. | 101 (25·1%) | 26 (22·0%) | .. | 99 (10·2%) | 62 (10·2%) | .. | ||
| Median age, years | 1 (0·7–1·1) | 1 (0·8–1·3) | 1 (0·9–1·2) | 0·21 | 57 (46–61) | 56 (48–62) | 0·21 | 77 (71–85) | 78 (71–84) | 0·96 | ||
| Sex | .. | .. | .. | 0·28 | .. | .. | 0·0061 | .. | .. | 0·39 | ||
| Male | 174 (45·1%) | 77 (39·9%) | 35 (50·0%) | .. | 182 (45·3%) | 71 (60·2%) | .. | 568 (58·6%) | 343 (56·3%) | .. | ||
| Female | 212 (54·9%) | 116 (60·1%) | 35 (50·0%) | .. | 220 (54·7%) | 47 (39·8%) | .. | 401 (41·4%) | 266 (43·7%) | .. | ||
| Smoking status | .. | .. | .. | NA | .. | 0·11 | .. | .. | <0·0001 | |||
| Current smoker | NA | NA | NA | .. | 121 (30·1%) | 26 (22·0%) | .. | 471 (48·6%) | 209 (34·3%) | .. | ||
| Non-smoker | NA | NA | NA | .. | 281 (69·9%) | 92 (78·0%) | .. | 498 (51·4%) | 400 (65·7%) | .. | ||
| Number of pre-existing medical conditions† | .. | .. | .. | 0·17 | .. | .. | 0·0425 | .. | .. | 0·0023 | ||
| None | 276 (71·5%) | 123 (63·7%) | 46 (65·7%) | .. | NA | NA | .. | 226 (23·3%) | 94 (15·4%) | .. | ||
| 1 | 107 (27·7%) | 65 (33·7%) | 23 (32·9%) | .. | 103 (25·6%) | 34 (28·8%) | .. | 325 (33·5%) | 222 (36·5%) | .. | ||
| 2 | 3 (0·8%) | 3 (1·6%) | 0 | .. | 90 (22·4%) | 14 (11·9%) | .. | 246 (25·4%) | 167 (27·4%) | .. | ||
| ≥3 | 0 | 2 (1·0%) | 1 (1·4%) | .. | 209 (52·0%) | 70 (59·3%) | .. | 172 (17·8%) | 126 (20·7%) | .. | ||
| At least one pre-existing medical condition† | 106 (27·5%) | 65 (33·7%) | 22 (31·4%) | 0·29 | 402 (100%) | 118 (100%) | NA | 749 (77·3%) | 516 (84·7%) | 0·0006 | ||
| Type of pre-existing medical condition | .. | .. | .. | .. | .. | .. | .. | .. | .. | .. | ||
| Obesity | 3 (0·8%) | 0 | 2 (2·9%) | 0·0329 | 95 (23·6%) | 25 (21·2%) | 0·67 | 100 (10·3%) | 58 (9·5%) | 0·67 | ||
| Asthma | 51 (13·2%) | 50 (25·9%) | 11 (15·7%) | <0·0001 | 67 (16·7%) | 38 (32·2%) | <0·0001 | 175 (18·1%) | 145 (23·8%) | 0·0079 | ||
| Diabetes | 0 | 0 | 0 | NA | 107 (26·6%) | 38 (32·2%) | 0·28 | 265 (27·3%) | 174 (28·6%) | 0·64 | ||
| Metabolic condition | 0 | 0 | 0 | NA | 91 (22·6%) | 36 (30·5%) | 0·0535 | 155 (16·0%) | 132 (21·7%) | 0·31 | ||
| Cardiomyopathy | 68 (17·6%) | 52 (26·9%) | 14 (20·0%) | 0·0342 | 88 (21·9%) | 21 (17·8%) | 0·41 | 261 (26·9%) | 156 (25·6%) | 0·60 | ||
| Immune system disorder | 7 (1·8%) | 4 (2·1%) | 1 (1·4%) | 0·94 | 58 (14·4%) | 14 (11·9%) | 0·58 | 119 (12·3%) | 71 (11·7%) | 0·77 | ||
| Immunosuppressing condition‡ | 0 | 0 | 1 (1·4%) | 0·0323 | 53 (13·2%) | 7 (5·9%) | 0·0512 | 114 (11·8%) | 69 (11·3%) | 0·85 | ||
| Neurological condition | 83 (21·5%) | 31 (16·1%) | 19 (27·1%) | 0·11 | 76 (18·9%) | 29 (24·6%) | 0·22 | 231 (23·8%) | 167 (27·4%) | 0·12 | ||
| Renal condition | 3 (0·8%) | 4 (2·1%) | 1 (1·4%) | 0·41 | 62 (15·4%) | 29 (24·6%) | 0·0218 | 90 (9·3%) | 65 (10·7%) | 0·42 | ||
| Liver condition | 6 (1·6%) | 0 | 0 | 0·13 | 25 (6·2%) | 3 (2·5%) | 0·19 | 12 (1·2%) | 6 (1·0%) | 0·83 | ||
| Previous influenza vaccination | .. | .. | .. | NA | .. | .. | <0·0001 | .. | .. | <0·0001 | ||
| Yes | NA | NA | NA | .. | 44 (10·9%) | 84 (71·2%) | .. | 192 (19·8%) | 482 (79·1%) | .. | ||
| No | NA | NA | NA | .. | 358 (89·1%) | 34 (28·8%) | .. | 777 (80·2%) | 127 (20·9%) | .. | ||
| Antiviral medication use | .. | .. | .. | <0·0001 | .. | .. | 0·50 | .. | .. | 0·0213 | ||
| Any antiviral medication use | 106 (27·5%) | 80 (41·5%) | 28 (40·0%) | .. | 231 (57·5%) | 63 (53·4%) | .. | 493 (50·9%) | 348 (57·1%) | .. | ||
| ≤2 days after symptom onset | 24 (6·2%) | 18 (9·3%) | 7 (10·0%) | 0·0112§ | 85 (21·1%) | 25 (21·2%) | 0·16§ | 155 (16·0%) | 102 (16·7%) | 0·0931§ | ||
| ≥3 days after symptom onset | 35 (9·1%) | 27 (14·0%) | 7 (10·0%) | .. | 130 (32·3%) | 29 (24·6%) | .. | 218 (22·5%) | 155 (25·5%) | .. | ||
| No antiviral medication use | 280 (72·5%) | 113 (58·5%) | 42 (60·0%) | .. | 171 (42·5%) | 55 (46·6%) | .. | 476 (49·1%) | 261 (42·9%) | .. | ||
| Time from symptom onset to admission, days | .. | .. | .. | 0·71 | .. | .. | 0·95 | .. | .. | 0·19 | ||
| 0 | 77 (19·9%) | 40 (20·7%) | 8 (11·4%) | .. | 108 (26·9%) | 30 (25·4%) | .. | 201 (20·7%) | 153 (25·1%) | .. | ||
| 1–2 | 127 (32·9%) | 63 (32·6%) | 27 (38·6%) | .. | 132 (32·8%) | 42 (35·6%) | .. | 340 (35·1%) | 213 (35·0%) | .. | ||
| 3–4 | 98 (25·4%) | 46 (23·8%) | 20 (28·6%) | .. | 92 (22·9%) | 27 (22·9%) | .. | 235 (24·3%) | 134 (22·0%) | .. | ||
| 5–10 | 84 (21·8%) | 44 (22·8%) | 15 (21·4%) | .. | 70 (17·4%) | 19 (16·1%) | .. | 193 (19·9%) | 109 (17·9%) | .. | ||
| Influenza virus type and subtype of infection | .. | .. | .. | 0·96 | .. | .. | 0·54 | .. | .. | 0·12 | ||
| Influenza A | 311 (80·6%) | 157 (81·3%) | 56 (80·0%) | .. | 361 (89·8%) | 103 (87·3%) | .. | 853 (88·0%) | 519 (85·2%) | .. | ||
| H3N2 | 126 (32·6%) | 76 (39·4%) | 26 (37·1%) | .. | 173 (43·0%) | 53 (44·9%) | .. | 522 (53·9%) | 348 (57·1%) | .. | ||
| H1N1 | 169 (43·8%) | 74 (38·3%) | 27 (38·6%) | .. | 188 (46·8%) | 50 (42·4%) | .. | 316 (32·6%) | 162 (26·6%) | .. | ||
| No subtype available | 16 (4·1%) | 7 (3·6%) | 3 (4·3%) | .. | 0 | 0 | .. | 15 (1·5%) | 9 (1·5%) | .. | ||
| Influenza B | 75 (19·4%) | 36 (18·7%) | 14 (20·0%) | .. | 41 (10·2%) | 15 (12·7%) | .. | 116 (12·0%) | 90 (14·8%) | .. | ||
| Yamagata | 13 (3·4%) | 10 (5·2%) | 5 (7·1%) | .. | 28 (7·0%) | 12 (10·2%) | .. | 41 (4·2%) | 42 (6·9%) | .. | ||
| Victoria | 15 (3·9%) | 8 (4·1%) | 2 (2·9%) | .. | 6 (1·5%) | 2 (1·7%) | .. | 13 (1·3%) | 16 (2·6%) | .. | ||
| No lineage information | 47 (12·2%) | 18 (9·3%) | 7 (10·0%) | .. | 7 (1·7%) | 1 (0·8%) | .. | 62 (6·4%) | 32 (5·3%) | .. | ||
| Viral coinfection detected | .. | .. | .. | 0·10 | .. | .. | 0·80 | .. | .. | 0·97 | ||
| Yes | 33 (8·5%) | 25 (13·0%) | 11 (15·7%) | .. | 3 (0·7%) | 0 | .. | 11 (1·1%) | 6 (1·0%) | .. | ||
| Respiratory syncytial virus | 30 (7·8%) | 20 (10·4%) | 11 (15·7%) | .. | 3 (0·7%) | 0 | .. | 1 (0·1%) | 1 (0·2%) | .. | ||
| Parainfluenza | 1 (0·3%) | 2 (1·0%) | 0 | .. | 0 | 0 | .. | 0 | 1 (0·2%) | .. | ||
| Human metapneumovirus | 2 (0·5%) | 1 (0·5%) | 0 | .. | 0 | 0 | .. | 1 (0·1%) | 2 (0·3%) | .. | ||
| Adenovirus | 0 | 1 (0·5%) | 0 | .. | 0 | 0 | .. | 5 (0·5%) | 0 | .. | ||
| Other viruses | 0 | 1 (0·5%) | 0 | .. | 0 | 0 | .. | 4 (0·4%) | 2 (0·3%) | .. | ||
| No | 353 (91·5%) | 168 (87·0%) | 59 (84·3%) | .. | 399 (99·3%) | 118 (100%) | .. | 958 (98·9%) | 603 (99·0%) | .. | ||
Data are n (%) or median (IQR), and summarise the characteristics from a single randomly selected imputed dataset. p values are from χ2 tests for categorical variables and Wilcoxon rank sum tests for continuous variables. NA=not applicable.
*
Full vaccination was defined as receipt of two doses of influenza vaccine for children aged 6–24 months; partial vaccination was defined as receipt of one dose of influenza vaccine more than 14 days before symptom onset; for 22 children with no information on dose two, we assumed partial vaccination.
†
Diagnosis of at least one of the following pre-existing medical conditions: asthma, diabetes, metabolic disorder, immune system disorder, nervous system disorder, renal disorder, and liver disorder.
‡
Immunosuppressing condition included use of immunosuppressing medications or receipt of transplant.
§
p values compare timing of antiviral medication use.