Table 1.

Summary of reports on phase 2/3 trials for COVID-19 vaccines.

Study	Characteristics of vaccine	Dosage	Dose interval	Placebo	Older groups included in the trial	No. of cases	% of older age group	No. of positive cases, %	No. of controls	% of older age group	No. of positive cases, %	Crude Efficacy
Baden et al., 2021[2]	mRNA-1273	100 μg × 2	28 days	Saline	≥ 65 years	14550	24.8%	19, 0.13%	14598	24.7%	269, 1.84%	93.03%
Polack et al., 2020 [3]	mRNA-BNT162b2	30 μg × 2	21 days	Saline	> 55 years	17397	43.1%	8, 0.05%	17498	43.1%	162, 0.93%	95.08%
Voysey et al., 2021 [4]	Replication- deficient chimpanzee adenovirus Ox1	2.2 × 10¹⁰ viral particles × 2	4 to 12 weeks	MenACWY	< 55 years	1367	-	3, 0.22%	1374	-	30, 2.18%	90.14%
		5 × 10¹⁰ viral particles × 2	28 days	MenACWY	≥ 55 years	2377	21.0%	15, 0.63%	2430	20.9%	38, 1.56%	60.03%
		3.5–6.5 × 10¹⁰ viral particles × 2	4 to 12 weeks	MenACWY + saline	≥ 55 years	2063	10.7%	12, 0.58%	2025	9.5%	33, 1.63%	64.68%
Voysey et al., 2021[5]		5 × 10¹⁰ viral particles × 2	4 to 12 weeks	Saline	≥ 55 years	1067	N/A	15, 1.41%	1017	N/A	91, 8.95%	85.49%
Logunov et al., 2021 [1]	Replication- deficient human adenoviruses rAd5 rAd26	10¹¹ viral particles × 2, first dose rAd26, second dose rAd5	21 days	Vaccine buffer	≥ 50 years	14964	34.2%	16, 0.11%	4902	34.3%	62, 1.26%	91.64%

Notes: crude efficacy was calculated as 1–Odds (OR) × 100, where the OR was calculated as OR = (a/b)/(c/d) = (a × d)/(b × c) where a is the number of vaccinated participants with COVID-19, b is the number of vaccinated participants without COVID-19, c is the number of unvaccinated participants with COVID-19, d is the number of unvaccinated participants without COVID-19. Figure were retrieved from reported studies; where not directly reported, corresponding estimates were reverse-calculated.