TABLE 3. Relative vaccine effectiveness of a single bivalent mRNA COVID-19 booster dose against symptomatic SARS-CoV-2 infection* received after 2, 3, or 4 monovalent vaccine doses, by age group, number of monovalent COVID-19 vaccine doses received, and interval since last monovalent dose — Increasing Community Access to Testing program, United States, September–November 2022.
| Age group, yrs/mos since receipt of most recent monovalent dose | Relative VE (95% CI), by no. of monovalent doses received† |
|||
|---|---|---|---|---|
| 2 doses | 3 doses | 4 doses§ | ≥2 doses | |
|
18–49
| ||||
| 2–3 |
45 (31–56) |
24 (14–33) |
NA |
30 (22–37) |
| 4–5 |
47 (35–57) |
41 (35–47) |
NA |
43 (38–48) |
| 6–7 |
42 (30–52) |
47 (42–52) |
NA |
46 (41–50) |
| ≥8 |
53 (45–60) |
58 (56–61) |
NA |
56 (53–58) |
|
50–64
| ||||
| 2–3 |
— |
15 (–4–31) |
33 (24–41) |
31 (24–38) |
| 4–5 |
44 (18–62) |
31 (18–42) |
36 (29–43) |
36 (30–41) |
| 6–7 |
46 (22–62) |
36 (25–45) |
40 (32–47) |
38 (32–43) |
| ≥8 |
61 (49–70) |
51 (45–55) |
NA |
48 (45–51) |
|
≥65
| ||||
| 2–3 |
— |
— |
32 (23–40) |
28 (19–35) |
| 4–5 |
— |
21 (1–36) |
36 (29–42) |
33 (27–39) |
| 6–7 |
— |
14 (–6–30) |
40 (33–46) |
36 (29–41) |
| ≥8 | 45 (27–58) | 42 (35–48) | NA | 43 (39–46) |
Abbreviations: NA = not applicable; VE = vaccine effectiveness.
* VE estimates with 95% CIs >50 percentage points are not shown because of imprecision.
† Total number of monovalent doses received for persons who did and did not receive a bivalent booster dose.
§ Persons aged <50 years without moderate or severe immunocompromise were not eligible for a fourth monovalent (second booster) dose. Because of timing of authorization, not enough persons ≥8 months from the fourth dose (second booster) were available to include in analyses.