TABLE 2. mRNA COVID-19 vaccine effectiveness* against laboratory-confirmed COVID-19–associated† emergency department and urgent care encounters and hospitalizations among adults aged ≥18 years, by Omicron–predominant period, age group, number and timing of vaccine doses,§ and median interval since last dose — VISION Network, 10 states, December 2021–June 2022.
| Encounter type | Omicron BA.1–predominant period¶ |
Omicron BA.2/BA.2.12.1–predominant period** |
||||||
|---|---|---|---|---|---|---|---|---|
| Total | No. (%) of positive test results† | Median interval since last dose, days (IQR) | VE %* (95% CI) | Total | No. (%) of positive test results† | Median interval since last dose days (IQR) | VE %* (95% CI) | |
|
ED or UC, age group (days since last dose)
| ||||||||
|
All ages, yrs
| ||||||||
| Unvaccinated (Ref) |
51,359
|
23,175 (45.1) |
— |
— |
27,907
|
3,501 (12.6) |
— |
— |
| 2 doses (14–149) |
7,286
|
2,377 (32.6) |
107 (76–129) |
47 (44–50) |
1,774
|
110 (6.2) |
104 (71–128) |
51 (38–60) |
| 2 doses (≥150) |
32,740
|
11,365 (34.7) |
267 (232–306) |
39 (37–41) |
20,883
|
2,584 (12.4) |
352 (278–398) |
12 (7–17) |
| 3 doses (7–119) |
29,333
|
3,667 (12.5) |
66 (41–89) |
84 (83–85) |
9,142
|
441 (4.8) |
94 (72–108) |
56 (51–61) |
| 3 doses (≥120) |
3,315
|
217 (6.5) |
132 (125–142) |
73 (68–77) |
26,654
|
3,186 (11.9) |
166 (145–190) |
26 (21–30) |
|
18–49 yrs
| ||||||||
| Unvaccinated (Ref) |
33,003
|
14,236 (43.1) |
— |
— |
18,429
|
2,269 (12.3) |
— |
— |
| 2 doses (14–149) |
4,909
|
1,621 (33.0) |
106 (76–129) |
40 (36–44) |
1,192
|
75 (6.3) |
105 (72–129) |
47 (31–60) |
| 2 doses (≥150) |
16,313
|
5,918 (36.3) |
252 (220–288) |
24 (21–28) |
11,203
|
1,427 (12.7) |
332 (254–379) |
7 (0–14) |
| 3 doses (7–119) |
8,755
|
1,259 (14.4) |
55 (33–79) |
76 (75–78) |
4,132
|
207 (5.0) |
91 (69–107) |
55 (47–62) |
| 3 doses (≥120) |
426
|
39 (9.2) |
130 (124–141) |
29 (−1–50) |
7,613
|
1,096 (14.4) |
159 (140–182) |
17 (10–25) |
|
≥50 yrs
| ||||||||
| Unvaccinated (Ref) |
18,356
|
8,939 (48.7) |
— |
— |
9,478
|
1,232 (13.0) |
— |
— |
| 2 doses (14–149) |
2,377
|
756 (31.8) |
109 (77–129) |
59 (54–63) |
582
|
35 (6.0) |
102 (68–128) |
59 (40–71) |
| 2 doses (≥150) |
16,427
|
5,447 (33.2) |
283 (248–316) |
52 (50–54) |
9,680
|
1,157 (11.9) |
376 (319–414) |
18 (10–26) |
| 3 doses (7–119) |
20,578
|
2,408 (11.7) |
71 (46–93) |
87 (86–88) |
5,010
|
234 (4.7) |
96 (73–109) |
58 (51–64) |
| 3 doses (≥120) |
2,889
|
178 (6.2) |
133 (125–143) |
81 (77–84) |
19,041
|
2,090 (11.0) |
170 (147–193) |
32 (26–38) |
| 4 doses (≥7)†† |
N/A
|
— |
— |
— |
4,094
|
355 (8.7) |
28 (17–42) |
66 (60–71) |
|
Hospitalization, age group (days since last dose)
| ||||||||
|
All ages, yrs
| ||||||||
| Unvaccinated (Ref) |
14,742
|
6,829 (46.3) |
— |
— |
6,682
|
494 (7.4) |
— |
— |
| 2 doses (14–149) |
1,236
|
297 (24.0) |
105 (73–129) |
68 (63–73) |
343
|
12 (3.5) |
102 (71–128) |
57 (19–77) |
| 2 doses (≥150) |
8,850
|
2,542 (28.7) |
289 (252–322) |
61 (58–63) |
5,118
|
393 (7.7) |
371 (308–413) |
24 (12–35) |
| 3 doses (7–119) |
9,146
|
786 (8.6) |
72 (47–93) |
92 (91–93) |
2,350
|
72 (3.1) |
94 (74–108) |
69 (58–76) |
| 3 doses (≥120) |
1,425
|
80 (5.6) |
132 (125–142) |
85 (81–89) |
7,686
|
519 (6.8) |
168 (146–191) |
52 (44–59) |
|
18–49 yrs§§
| ||||||||
| Unvaccinated (Ref) |
4,057
|
1,515 (37.3) |
— |
— |
—
|
— |
— |
— |
| 2 doses (14–149) |
392
|
83 (21.2) |
101 (67–127) |
64 (52–73) |
—
|
— |
— |
— |
| 2 doses (≥150) |
1,304
|
329 (25.2) |
258 (226–294) |
52 (43–59) |
—
|
— |
— |
— |
| 3 doses (7–119) |
812
|
53 (6.5) |
57 (36–81) |
91 (87–94) |
—
|
— |
— |
— |
| 3 doses (≥120) |
56
|
1 (1.8) |
133 (126–142) |
94 (62–99) |
—
|
— |
— |
— |
|
≥50 yrs§§
| ||||||||
| Unvaccinated (Ref) |
10,685
|
5,314 (49.7) |
— |
— |
4,595
|
393 (8.6) |
— |
— |
| 2 doses (14–149) |
844
|
214 (25.4) |
108 (76–129) |
71 (65–75) |
—
|
— |
— |
— |
| 2 doses (≥150) |
7,546
|
2,213 (29.3) |
294 (259–325) |
63 (60–66) |
4,139
|
352 (8.5) |
381 (325–418) |
22 (8–34) |
| 3 doses (7–119) |
8,334
|
733 (8.8) |
73 (49–94) |
92 (91–93) |
1,957
|
57 (2.9) |
95 (74–108) |
73 (63–81) |
| 3 doses (≥120) |
1,369
|
79 (5.8) |
132 (125–142) |
86 (82–89) |
7,113
|
480 (6.8) |
169 (147–191) |
55 (46–62) |
| 4 doses (≥7)†† | N/A | — | — | — | 1,204 | 74 (6.2) | 27 (17–41) | 80 (71–85) |
Abbreviations: ED = emergency department; ICD-9 = International Classification of Diseases, Ninth Revision; ICD-10 = International Classification of Diseases, Tenth Revision; N/A = not applicable; PHIX = Paso Del Norte Health Information Exchange; Ref = referent group; RT-PCR = reverse transcription–polymerase chain reaction; UC = urgent care; VE = vaccine effectiveness.
* VE was calculated as ([1−odds ratio] x 100%), estimated using a test-negative design, adjusted for age, geographic region, calendar time (days since January 1, 2021), and local virus circulation (percentage of SARS-CoV-2–positive results from testing within the counties surrounding the facility on the date of the encounter) and weighted for inverse propensity to be vaccinated or unvaccinated (calculated separately for each set of VE estimates among ED or UC encounters and hospitalizations by Omicron–predominant period and age group). Generalized boosted regression trees were used to estimate the propensity to be vaccinated based on sociodemographic characteristics, underlying medical conditions, and facility characteristics.
† Medical events with a discharge code consistent with COVID-19–like illness were included. COVID-19–like illness diagnoses included acute respiratory illness (e.g., respiratory failure or pneumonia) or related signs or symptoms (e.g., cough, fever, dyspnea, vomiting, or diarrhea) using ICD-9 and ICD-10 codes. Clinician-ordered molecular assays (e.g., real-time RT-PCR) for SARS-CoV-2 occurring ≤14 days before to <72 hours after the encounter date were included.
§ Vaccination was defined as having received the listed number of doses of an mRNA-based COVID-19 vaccine within the specified range of number of days before the medical event index date, which was the date of respiratory specimen collection associated with the most recent positive or negative SARS-CoV-2 test result before the medical event or the admission date if testing only occurred after the admission.
¶ Partners contributing data on medical events during dates of estimated ≥75% Omicron BA.1 predominance were in California (Dec 21, 2021–Mar 6, 2022), Colorado (Dec 25, 2021–Mar 12, 2022), Indiana (Dec 31, 2021–Mar 4, 2022), Minnesota and Wisconsin (Jan 1–Mar 5, 2022), New York (Dec 18, 2021–Feb 26, 2022), Oregon and Washington (Jan 1–Mar 12, 2022), Texas (Baylor Scott & White Health [Dec 18, 2021–Mar 5, 2022] and PHIX [Jan 8–Mar 19, 2022]), and Utah (Dec 27, 2021–Mar 19, 2022).
** Partners contributing data on medical events during dates of estimated ≥75% Omicron BA.2/BA.2.12.1 predominance were in California (Mar 25–Jun 10, 2022), Colorado (Apr 9–Jun 4, 2022), Indiana (Mar 19–Jun 10, 2022), Minnesota and Wisconsin (Apr 9–Jun 4, 2022), New York (Mar 26–Jun 10, 2022), Oregon and Washington (Apr 9–Jun 10, 2022), Texas (Baylor Scott & White Health [Mar 6–Jun 4, 2022 and PHIX [Apr 23–Jun 10, 2022]), and Utah (Mar 28–Jun 10, 2022).
†† For estimation of 4-dose mRNA VE among patients aged ≥50 years during the Omicron BA.2/BA.2.12.1–predominant period, unvaccinated patients whose medical event index date was before Apr 5, 2022 were excluded from the referent group (1,836 ED or UC encounters and 999 hospitalizations excluded among unvaccinated patients) because the earliest medical event index date included among 4-dose mRNA-vaccinated patients was 7 days after Mar 29, 2022 when a second booster mRNA vaccine dose (fourth dose) was first included in recommendations for adults aged ≥50 years (at least 4 months after receiving a third mRNA dose).
§§ VE estimates with 95% CIs >50 percentage points are not shown because of imprecision.