TABLE 2. COVID-19 vaccine effectiveness among health care personnel case-patients and controls, by number of COVID-19 vaccine doses received before SARS-CoV-2 test date — 33 U.S. sites, January–March 2021.
| Interval from dose to test date | No. (%) |
Vaccine effectiveness†
% (95% CI) |
||
|---|---|---|---|---|
| Case-patients* (N = 623) | Controls* (N = 1,220) | Unadjusted | Adjusted§ | |
|
Dose 1
| ||||
| ≥14 days |
64 (10) |
241 (20) |
82.2 (75.1–87.3) |
81.7 (74.3–86.9) |
|
Dose 2
| ||||
| ≤2 days |
5 (<1) |
109 (9) |
||
| 3–6 days |
16 (3) |
85 (7) |
||
| ≥7 days | 19 (3) | 184 (15) | 93.4 (86.4–96.8) | 93.5 (86.5–96.9) |
Abbreviations: CI = confidence interval; HCP = health care personnel; mOR = matched odds ratio; OR = odds ratio; PCR = polymerase chain reaction; VE = vaccine effectiveness.
* Case-patients: HCP who received positive SARS-CoV-2 PCR or antigen-based test results and had one or more symptoms of COVID-19–like illness; controls: HCP who received negative SARS-CoV-2 PCR test results.
† VE (Pfizer-BioNTech and Moderna) was estimated using a conditional logistic regression model accounting for matching by site of enrollment and week of test date.
§ OR used in conditional logistic regression model to calculate VE was adjusted for age, race, and presence of underlying conditions: VE = 100% × (1−mOR).