A phase 1, randomized, placebo-controlled study to evaluate the safety and immunogenicity of an mRNA-based RSV prefusion F protein vaccine in healthy younger and older adults

Figures & data

Figure 1. Participant Disposition for Group A, Younger Adults

Figure 2. Participant Disposition for Group B, Older Adults

Table 1. Participant baseline characteristics: randomized cohorts, Part A and Part B

	Part A; Younger Adults				Part B; Older Adults
	mRNA-1777 (V171)			Placebo	mRNA-1777 (V171)				Placebo
	25 µg	100 µg	200 µg		25 µg	100 µg	200 µg	300 µg
No. of Participants	(N = 18)	(N = 18)	(N = 18)	(N = 18)	(N = 9)	(N = 24)	(N = 24)	(N = 23)	(N = 27)
Age, mean years	27.5	28	28.5	30.8	64.7	66.9	67.7	66.9	66.8
Age (range)	18–41	19–47	19–47	19–47	60–69	60–78	60–79	60–78	60–77
Sex, n, male (%)	17 (94.4)	18 (100)	18 (100)	18 (100)	3 (33.3)	10 (41.7)	12 (50.0)	10 (43.5)	10 (37.0)
Race, n, white (%)	16 (88.9)	16 (88.9)	14 (77.8)	17 (94.4)	9 (100.0)	23 (95.8)	22 (91.7)	23 (100)	27 (100)
Race, n, Asian or multi (%)	2 (11.1)	2 (11.1)	4 (22.2)	1 (5.6)	0	1 (4.2)	2 (8.3)	0	0
BMI, mean kg/m^2	25.3	24.8	24.1	23.9	26.9	27.5	26.7	26.6	24.9

BMI = Body Mass Index, multi = multiple races

Table 2. Summary of treatment-emergent adverse events

	mRNA-1777 (V171)-Younger Adults					mRNA-1777 (V171)-Older Adults
	25 µg	100 µg	200 µg	Overall	Placebo	25 µg	100 µg	200 µg	300 µg	Overall	Placebo
Safety Set	(N = 18)	(N = 18)	(N = 18)	(N = 54)	(N = 18)	(N = 9)	(N = 24)	(N = 24)	(N = 23)	(N = 80)	(N = 27)
Any TEAE	16 (88.9)	18 (100)	18 (100)	52 (96.3)	15 (83.3)	9 (100)	24 (100)	24 (100)	23 (100)	80 (100)	24 (88.9)
Any treatment-related TEAE	15 (83.3)	18 (100)	18 (100)	51 (94.4)	8 (44.4)	8 (88.9)	24 (100)	23 (95.8)	22 (95.7)	77 (96.3)	10 (37.0)
Any SAE	0	0	1 (5.6)	1 (5.6)	0	2 (22.2)	1 (4.2)	3 (12.5)	0	6 (7.5)	2 (7.4)
Any treatment-related SAE	0	0	0	0	0	0	0	0	0	0	0
Death	0	0	0	0	0	0	0	0	0	0	1 (3.7)
Any TEAE leading to withdrawal	0	0	0	0	0	0	0	0	0	0	1 (3.7)
Any AE of special interest	0	0	0	0	0	0	0	0	0	0	0
Any new onsets of chronic illness	0	0	0	0	0	0	0	0	0	0	0
Any medically attended AE	7 (38.9)	7 (38.9)	6 (33.3)	20 (37.0)	7 (38.9)	7 (77.8)	12 (50.0)	8 (33.3)	11 (47.8)	38 (47.5)	17 (63.0)
Any new onset of AID	0	0	0	0	0	0	0	0	0	0	0

Abbreviations: AE, adverse event; SAE, serious adverse event; TEAE, treatment-emergent adverse event, AID = autoimmune disorder. A TEAE was defined as any event not present before exposure to investigational product or any event already present that worsened in intensity or frequency after exposure including solicited and unsolicited AEs. A subject was counted once within each AE category if the subject reported 1 or more events. Percentages were based on the number of participants who received the specified treatment and overall.

Figure 3. Solicited Injection-Site Adverse Events

Adverse events collected Days 1–7 post-vaccination from the safety set is shown with grade level. The height of the stacked bar represents the total percentage of participants reporting the adverse event. The grade levels within the bar indicate the proportion of the total attributed to each.

Figure 4. Solicited Systemic Adverse Events

Solicited Systemic Adverse events collected Days 1–7 post-vaccination from the safety set is displayed as the percentage of participants reporting each adverse event. The height of the stacked bar represents the total percentage of participants reporting the adverse event. The grade levels within the bar indicate the proportion of the total attributed to each.

Figure 5. Serum Neutralization Titers against RSV A and RSV B

Serum neutralization GMTs for RSV A (Panel A) and RSV B (Panel B), and GMFIs for RSV A (Panel C) and RSV B (Panel D) by time. Per-protocol population is shown. Error bars represent the 95% confidence intervals.

Figure 6. Serum Antibody Titers to Prefusion F Protein

Serum antibody GMTs (Panel A) and GMFIs (Panel B) by time. Per-protocol population is shown. Error bars represent the 95% confidence intervals.

Figure 7. D25 and Palivizumab Competing Antibodies

Geometric fold increases (GMFI) in D25 (Panel A) or palivizumab competing antibodies (Panel B) over baseline levels by time. Per-protocol population is shown. Error bars represent the 95% confidence intervals.

Figure 8. IFN-γ ELISPOT

IFN-γ ELISPOT responses in spot forming cells per million peripheral blood mononuclear cells (PBMC) are shown for the Younger Adults (Panel A) and Older Adults (Panel B). ELISPOT graphs display the per-protocol group mean and 95% confidence intervals by Day.

Figure 9. CD4 T cell-responses by Intracellular Cytokine Staining

The percentage of CD4 T-cells positive for IFN-γ, IL-2 or TNF-α as measured in intracellular cytokine staining are shown for the Younger Adults (Panel A) and Older Adults (Panel B) by Day. Intracellular staining graphs display the per-protocol group mean and 95% confidence interval.