Table 3.
Risk Ratios for Preterm and Small-for-Gestational-Age Births After Monovalent Influenza Vaccine Receipt Among Study Participants (n = 46,549), by Timing of Vaccination and Model Specification, Vaccine Safety Datalink Cohort, 2009–2010
| Modela | Outcome by Period of
Vaccination |
|||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Preterm Birth (<37 Weeks) |
SGA Birth (<10th Percentile) |
|||||||||||||||
| Any Time During Pregnancy |
First Trimester |
Second Trimester |
Third Trimester |
Any Time During Pregnancy |
First Trimester |
Second Trimester |
Third Trimester |
|||||||||
| RR | 95% CI | RR | 95% CI | RR | 95% CI | RR | 95% CI | RR | 95% CI | RR | 95% CI | RR | 95% CI | RR | 95% CI | |
| 1 | 0.79 | 0.74, 0.85 | 0.85 | 0.77, 0.93 | 0.87 | 0.79, 0.95 | 0.63 | 0.55, 0.72 | 0.97 | 0.91, 1.03 | 0.88 | 0.80, 0.96 | 1.03 | 0.95, 1.12 | 0.99 | 0.89, 1.10 |
| 2 | 0.88 | 0.82, 0.94 | 0.84 | 0.76, 0.93 | 0.87 | 0.79, 0.96 | 0.83 | 0.73, 0.96 | NA | NA | NA | NA | NA | NA | NA | NA |
| 3 | 0.91 | 0.84, 0.98 | 0.87 | 0.78, 0.97 | 0.90 | 0.81, 1.00 | 0.97 | 0.82, 1.14 | 0.99 | 0.93, 1.06 | 0.88 | 0.80, 0.96 | 1.03 | 0.95, 1.12 | 1.10 | 0.96, 1.25 |
| 4 | 0.92 | 0.84, 1.00 | 0.88 | 0.79, 0.98 | 0.90 | 0.80, 1.01 | 1.0 | 0.85, 1.20 | 1.0 | 0.93, 1.08 | 0.90 | 0.82, 0.99 | 1.08 | 0.98, 1.20 | 1.11 | 0.96, 1.28 |
| 5 | 0.91 | 0.83, 1.00 | 0.87 | 0.78, 0.97 | 0.89 | 0.79, 1.00 | 1.0 | 0.83, 1.20 | 1.0 | 0.93, 1.08 | 0.90 | 0.82, 0.99 | 1.08 | 0.98, 1.20 | 1.11 | 0.96, 1.27 |
Abbreviations: CI, confidence interval; NA, not applicable; RR, relative risk; SGA, small-for-gestational-age.
a Model 1 was the naïve model. Model 2 was adjusted for the time-dependent monovalent vaccine exposure. Model 3 was adjusted for the factors in model 2 and for temporal access to vaccination. Model 4 was adjusted for the factors in model 3 and for propensity of vaccination. Model 5 was adjusted for the factors in model 4 and H1N1 circulation.