Immunogenicity and safety of boosting with a recombinant two-component SARS-CoV-2 vaccine: two randomized, parallel-controlled, phase 2 studies

Figures & data

Figure 1. Flow diagram of study-1 (panel A) and study-2 (panel B).

ReCOV HA: pilot batch of ReCOV. ReCOV TC: commercial batch of ReCOV.

In Study-1, all subjects were assessed immune response at baseline, 14 days, 28 days, 3 months, and 6 months. In Study-2, all subjects were assessed immune response at baseline and 14 days, while only the first 100 randomized subjects (50 each of ReCOV TC group and BNT162b2 group, respectively) were assessed for immune durability at 28 days, 3 months, and 6 months post boosting.

Figure 1. (Continued).

Table 1. Subjects demographic characteristics of study-1 and study-2.

	Study-1 (mITT set)			Study-2 (mITT set)
Variable Category	0.5 mL COVILO® (N = 103)	20 μg ReCOV (N = 98)	40 μg ReCOV (N = 99)	30 μg COMIRNATY® (N = 199)	20 μg ReCOV HA (N = 199)	20 μg ReCOV TC (N = 202)
Age (years), Mean (SD)	27.2 (6.37)	27.8 (6.5)	27.4 (5.91)	35.9 (12.32)	34.8 (12.32)	36.9 (12.36)
Sex, n (%)
Female	0	1 (1.0)	0	91 (45.7)	96 (48.2)	100 (49.5)
Male	103 (100.0)	97 (99.0)	99 (100.0)	108 (54.3)	103 (51.8)	102 (50.5)
Race, n (%)
Asian	102 (99.0)	98 (100.0)	98 (99.0)	199 (100)	199 (100)	202 (100)
Other	1 (1.0)	0	1 (1.0)	0	0	0
Ethnicity, n (%)
Not Hispanic or Latino	103 (100.0)	98 (100.0)	98 (99.0)	199 (100)	199 (100)	202 (100)
Doses of previous vaccination, n (%)
2 Doses	95 (92.2)	93 (94.9)	91 (91.9)	199 (100)	199 (100)	202 (100)
3 Doses	8 (7.8)	5 (5.1)	8 (8.1)	0	0	0
Duration between the last dose of previous vaccination and the study vaccination, n (%)
90–180 days	14 (13.6)	11 (11.2)	12 (12.1)	7 (3.5)	7 (3.5)	8 (4.0)
181–365 days	89 (86.4)	87 (88.8)	87 (87.9)	192 (96.5)	192 (96.5)	194 (96.0)

N = Total number of subjects in the relevant analysis set. n = Number of subjects in each category. % = Percentage of subject in each category calculated relative to the number of subjects in corresponding analysis set. SD: Standard Deviation. ReCOV HA: pilot batch of ReCOV. ReCOV TC: commercial batch of ReCOV.

For both studies, the definition of modified Intent-to Treat (mITT): According to the Intention-To-Treat Principle, the mITT analysis set was defined as all randomized subjects.

who had received study vaccination.

Figure 2. GMTs of live-virus neutralizing antibody against SARS-CoV-2 prototype in study-1 (panel A) and study-2 (panel B).

The GMTs of neutralizing antibody at baseline and 14 days (d14) post boosting were illustrated for the study population of Study-1 (Panel A) and Study-2 (Panel B).

ReCOV HA: pilot batch of ReCOV. ReCOV TC: commercial batch of ReCOV.

*p-value <0.0001.

Figure 3. GMTs of pseudovirus neutralizing antibody against SARS-CoV-2 prototype and omicron variants in study-1 (panel A) and study-2 (panel B).

The GMTs of pseudovirus NAb against SARS-CoV-2 prototype, Omicron BA.2, BA.4/5, and BA.2.75 for Study-1; SARS-CoV-2 prototype, Omicron BA.4/5, BA.2.75, and BF.7 for Study-2, at baseline and 14 days (d14) post boosting were illustrated for relevant studies.

ReCOV HA: pilot batch of ReCOV. ReCOV TC: commercial batch of ReCOV.

Figure 4. (Continued).

Figure 4. Frequency of any related adverse events, solicited local and systemic adverse eveIn study-1 (panel A) and study-2 (panel B).

ReCOV HA: pilot batch of ReCOV. ReCOV TC: commercial batch of ReCOV. AE: adverse event.

In Study-1, the p-values for incidences of related AE, solicited local AE, and solicited systemic AE among the 3 vaccination groups were 0.038, 0.005, and 0.123, respectively, which suggested the statistical difference in incidences of related AE and solicited local AE between at least 2 vaccination groups.

In Study-2, the p-values for incidences of related AE, solicited local AE, and solicited systemic AE between ReCOV TC group and COMIRNATY® group were 0.251, 0.750, and 0.026, respectively, the p-values for relevant incidences between ReCOV HA and TC groups were 0.251, 0.370, and 0.018, which showed the incidence of solicited systemic AE was significantly higher in ReCOV TC group than that in ReCOV HA group or COMIRNATY® group.