Table 1 Characteristics of included RCTs
Studies | Blinding | Vaccines | Number of participants that received the first dose | Number of participants that received the second dose (seronegative, used to efficiency calculation) | Mean age [years] | Age | Sex [% of male] | Phase | Time between doses [days] | Observation time (used to efficiency calculation) |
|---|---|---|---|---|---|---|---|---|---|---|
mRNA vaccines | ||||||||||
Baden et al. 2021 [12] | Observer-blinded | mRNA-1273 | VG: (n = 15,181) PG: (n = 15,170) | VG: (n = 14,134) PG: (n = 14,073) | 51.4 | \(\ge\) 18 years | 52.7% | 3 | 28 | At least 14 days after the second dose |
El Sahly et al. 2021 [13] | Part A: observer-blinded Part B: open-label | mRNA-1273 | VG: (n = 15,180) PG: (n = 15,166) | VG: (n = 14,287) PG: (n = 14,264) | 51.4 | \(\ge\) 18 years | 52.6% | 3 | 28 | At least 14 days after the second dose |
Ali et al. 2021 [14] | Observer-blinded | mRNA-1273 | VG: (n = 2486) PG: (n = 1240) | VG: (n = 2139) PG: (n = 1042) | 14.3 | 12–17 years | 51% | 2/3 | 28 | At least 14 days after the second dose |
Polack et al. 2020 [11] | Observer-blinded | BNT162b2 | VG: (n = 18,860) PG: (n = 18,846) | VG: (n = 18,198) PG: (n = 18,325) | 52 | \(\ge\) 16 years | 50.6% | 2/3 | 21 | At least 7 days after the second dose |
Thomas et al. 2021 [15] | Observer-blinded | BNT162b2 | VG: (n = 22,030) PG: (n = 22,030) | VG: (n = 20,998) PG: (n = 21,096) | 51 | \(\ge\) 16 years//12–15 years | 51% | 2/3 | 21 | At least 7 days after the second dose |
Frenck et al. 2021 [16] | Observer-blinded | BNT162b2 | VG: (n = 1131) PG: (n = 1129) | VG: (n = 1005) PG: (n = 978) | 13.6 | 12–15 years | 51% | 3 | 21 | At least 7 days after the second dose |
Viral vector vaccines | ||||||||||
Voysey et al. 2021 [22] | Single-blind | ChAdOx1 nCoV-19 | NA | VG: (n = 1367) CG: (n = 1374) | NA | 18–55 years | VG: 35.2% CG: 32.5% | 2/3 | 4–6 weeks | At least 14 days after the second dose |
Single-blind | ChAdOx1 nCoV-19 | NA | VG: (n = 2377) CG: (n = 2430) | NA | \(\ge\) 18 years | VG: 42% CG: 40% | 2/3 | 4–6 weeks | At least 14 days after the second dose | |
Single-blind | ChAdOx1 nCoV-19 | NA | VG: (n = 2063) CG: (n = 2025) | NA | \(\ge\) 18 years | VG: 38.9% CG: 42.9% | 3 | up to 12 weeks | At least 14 days after the second dose | |
Madhi et al. 2021 [19] | Double-blind | ChAdOx1 nCoV-19 | VG: (n = 1011) PG: (n = 1010) | VG: (n = 750) PG: (n = 717) | 30 | 18–65 years | 56.5% | 1b/2 | 21 to 35 | At least 14 days after the second dose |
Clemens et al. 2021 [20] | Single-blind | ChAdOx1 nCoV-19 | NA | VG: (n = 4772) CG: (n = 4661) | NA | \(\ge\) 18 years | VG: 44% CG: 46% | 3 | between 4 and 12 weeks | At least 15 days after the second dose |
Falsey et al. 2021 [21] | Double-blind | ChAdOx1 nCoV-19 | VG: (n = 21,583) PG: (n = 10,796) | VG: (n = 17,662) PG: (n = 8550) | 50.2 | 18–64 years and \(\ge\) 65 years | 55.6% | 3 | 4 weeks apart | At least 15 days after the second dose |
Sadoff et al. 2021 [18] | Double-blind | Ad26.COV2.S | VG: (n = 21,895) PG: (n = 21,888) | – | 52 | \(\ge\) 18 years | 54.9% | 3 | – | At least 14 days after administration |
At least 28 days after administration | ||||||||||
Logunov et al. 2021 [17] | Double-blind | rAd26 and rAd5 | VG: (n = 16,427) PG: (n = 5435) | VG: (n = 14,964) PG: (n = 4902) no information about serostatus | 45.3 | \(\ge\) 18 years | VG: 61.1% PG: 61.5% | 3 | 21 | At least 21 days after the first dose (day of dose 2) |
Inactivated vaccines | ||||||||||
Al Kaabi et al. 2021 [25] | Double-blind | WIV04 and HB02 | WIV04 group (N = 13,459), HB02 group (N = 13,465), in the alum-only group control (N = 13,458) | WIV04 group (N = 12,743), HB02 group (N = 12,726) and aluminum hydroxide (alum)–only control (N = 12,737) | 36.1 | \(\ge\) 18 years | 84.4% | 3 | 21 | At least 14 days after the second dose |
Fadlyana et al. 2021 [26] | Double-blind | CoronaVac | VG: (n = 811) PG: (n = 809) | VG: (n = 798) PG: (n = 804) | 35.5 | 18–59 years | 64.5% | 3 | 14 | At least 14 days after the second dose |
Tanriover et al. 2021 [27] | Double-blind | CoronaVac | VG: (n = 6646) PG: (n = 3568) | VG: (n = 6559) PG: (n = 3470) | 45 | 18–59 years | 57.8% | 3 | 14 | At least 14 days after the second dose |
Subunit vaccines | ||||||||||
Shinde et al. 2021 [23] | Observer-blinded | NVX-CoV2373 | VG: (n = 2199) PG: (n = 2188) | HIV-negative participants: VG: (n = 1281) PG: (n = 1255) | 32 | 18–84 years | 57% | 2a/b | 21 | At least 7 days after the second dose |
Heath et al. 2021 [24] | Observer-blinded | NVX-CoV2373 | VG: (n = 7569) PG: (n = 7570) | VG: (n = 7020) PG: (n = 7019) | 56 | 18–84 years | 51.6% | 3 | 21 | At least 7 days after the second dose |