Volume 17, Number 3—March 2011
Research
Swine Influenza Virus Antibodies in Humans, Western Europe, 2009
Nancy A. Gerloff, Jacques R. Kremer, Emilie Charpentier, Aurélie Sausy, Christophe M. Olinger, Pierre Weicherding, John Schuh, Kristien Van Reeth, and Claude P. Muller
Table 3
Neutralizing antibody reactivity against 3 influenza viruses in swine workers and controls, Luxembourg, 2008–2009*
| Virus (strain) and cutoff value | Swine workers, no. (%; 95% CI), n = 211 | Controls, no. (%; 95% CI), n = 224 | p value |
|---|---|---|---|
| Pandemic (H1N1) 2009 (A/Luxembourg/43/2009) | |||
| >10 | 46 (21.8; 16.8–27.9)† | 23 (10.3); 6.9–14.9)‡ | 0.001§ |
| >20 | 37 (17.5; 13–23.2)† | 16 (7.1; 4.4–11.3)‡ | 0.001§ |
| >40 | 31 (14.7; 10.6–20.1) | 12 (5.4; 3.1–9.1) | 0.002§ |
| >80 | 14 (6.6; 4–10.8) | 4 (1.8; 0.7–4.5) | 0.02§ |
| >160 | 6 (2.8; 1.3–6.06) | 0 (0; 0–1.2) | 0.033¶ |
| >320 |
5 (2.4; 1–5.4) |
0 (0; 0–1.2) |
0.061¶ |
| Avian-like SIV (H1N1) (A/swine/Belgium/1/98) | |||
| >10 | 66 (31.3) 25.4–37.8) | 59 (26.3; 21–32.5) | 0.289§ |
| >20 | 57 (27; 21.5–33.4) | 38 (17; 12.6–22.4) | 0.015§ |
| >40 | 39 (18.5; 13.8–24.3) | 12 (5.4; 3.1–9.1) | <0.001§ |
| >80 | 21 (10; 6.6–14.7) | 4 (1.8; 0.7–4.5) | <0.001§ |
| >160 | 9 (4.3; 2.3–7.9) | 1 (0.4; 0.1–2.5) | 0.019¶ |
| >320 |
4 (1.9; 0.7–4.8) |
1 (0.4; 0.1–2.5) |
0.331¶ |
| Seasonal influenza (H1N1) (A/Luxembourg/572/2008)# | |||
| >10 | 183 (87.1; 83–91.9) | 132 (59.7; 53.2–66) | <0.001§ |
| >20 | 125 (59.5; 52.8–65.9) | 76 (34.4; 28.4–40.9) | <0.001§ |
| >40 | 61 (29; 23.3–35.5) | 39 (17.6; 13.2–23.2) | 0.007§ |
| >80 | 21 (10; 6.6–14.9) | 17 (7.7; 4.8–12) | 0.500§ |
| >160 | 14 (6.7; 3.9–11) | 7 (3.2; 1.4–6.5) | 0.144§ |
| >320 | 11 (5.2; 2.9–9.2) | 4 (1.8; 0.5–4.7) | 0.093§ |
*Values are no. persons with antibodies. CI, confidence interval; SIV, swine influenza virus. Boldface indicates significance (p<0.05).
†p<0.05 when compared with swine workers against avian-like SIV (H1N1) of the same titer cutoff.
‡p<0.003 when compared with swine workers against avian-like SIV (H1N1) of the same titer cutoff.
§χ2 test on 2-way table.
¶z-test.
#Data for 210 swine workers, 221 controls.
