Table 2.
Estimated Vaccine Effectiveness Among Pregnant Women in Peru With Vaccination Status as a Time-Varying Covariate—PRIME Study, 2018
| Variable | Analysis With Follow up From Start of influenza Season Verified and Unverified Vaccination Status | Sensitivity Analysis With Follow up From When the First Participant Became Vaccinated | ||||
|---|---|---|---|---|---|---|
| Total | Unvaccinated | Vaccinateda | Total | Unvaccinated | Vaccinateda | |
| Person-days (Median, IQR) |
242 068 (127, 86–174) | 183 199 (91, 54–138) | 58 869 (61, 34–93) | 217 713 (112, 74–158) | 158 844 (76, 42–124) | 58 869 (61, 34–93) |
| Laboratory-confirmed influenza cases (n) | 76 | 67 | 9 | 72 | 63 | 9 |
| Incidence rate per 100 000 person-days | 31.4 | 36.6 | 15.3 | 33.1 | 39.7 | 15.3 |
| Adjusted VE* against all types of influenza (95% CI) | N/A | Ref | 22.0% (−64.1% to 62.9%) | N/A | Ref | 20.1% (−67.6% to 61.9%) |
| Influenza A/H1N1 cases | 66 | 59 | 7 | 65 | 58 | 7 |
| Adjusted VE* against only A/H1N1 (95% CI) | N/A | Ref | 15.9% (−87.1% to 62.2%) | N/A | Ref | 15.9% (−87.4% to 62.3%) |
Abbreviation: CI, confidence interval; IQR, interquartile range; N/A, not applicable; PRIME, Pregnancy and Influenza Multinational Epidemiologic; Ref, referent category; VE, vaccine effectiveness.
a
We classified participants as vaccinated 14 days after they had received the 2018 influenza vaccine.
*Adjusted for inverse probability treatment weight.