Table. Detection rate of Bordetella pertussis in women who participated in a randomized, double-blind, placebo-controlled trial of trivalent inactivated influenza vaccine.
95%CI: 95% confidence interval; PCR: polymerase chain reaction.
Archived DNA samples independently of clinical presentation were tested by real-time PCR for the presence of the multicopy pertussis insertion sequence (IS) IS4814; if IS481 cycle threshold values were <40, total nucleic acids were extracted from the corresponding achieved respiratory specimen using a NucliSENS easyMAG (bioMerieux) platform and re-tested for IS481 and in a duplex reaction for hIS1001 and pIS1001, and in a singleplex reaction for the pertussis toxin subunit S1 (ptxS1). Primers and probes used, and PCR results interpretation have been described4.
| Influenza vaccine N=1062a | Placebo N=1054a | Risk-Ratio (95%CI) | P value | |
|---|---|---|---|---|
| Participants with at least one specimen collected, no (%)b | 675 (63.6) | 686 (65.1) | 1.0 (0.9, 1.0) | 0.46 |
| Participants with at least one specimen tested by PCR for pertussis, no (%)b | 635 (59.8) | 652 (61.9) | 1.0 (0.9, 1.0) | 0.33 |
| Respiratory specimens collected | 1713 | 1870 | - | - |
| Respiratory specimens tested by PCR for pertussis, no (%)c | 1494 (87.2) | 1631 (87.2) | 1.0 (0.9, 1.0) | 0.99 |
| Pertussis PCR-positive cases, no (%)d | 11 (1.0)f | 26 (2.5)g | 0.4 (0.2, 0.8) | 0.012 |
| Pertussis PCR-indeterminate cases, no (%)e | 10 (0.9) | 16 (1.5) | 0.6 (0.3, 1.4) | 0.23 |
| Overall pertussis cases, no (%) | 21 (2.0) | 42 (4.0) | 0.5 (0.2, 0.7) | 0.007 |
Participants were followed-up by weekly active surveillance for any respiratory illness from the time of enrolment through pregnancy to 24- weeks post-partum. Pharyngeal specimens were collected by study staff at the time of respiratory illness visits to the study clinic.
Percentage calculated from total participants enrolled. Respiratory specimens only collected in participants presenting with a respiratory illness.
Percentage calculated from total specimens collected.
PCR reaction with cycle threshold values for the IS481 gene <35 or ≤35-<40 plus positive for the ptxS1 gene.
PCR reaction with cycle threshold values for the IS481 gene ≤35-<40 and negative for the ptxS1 gene.
One specimen also tested positive for influenza A/H1N1.
Two specimens also tested positive for influenza A/H3N2. One participant tested pertussis PCR-positive in two different specimens collected 22 days apart, only the first episode was included.