SummaryBackgroundNanocovax is a recombinant severe acute respiratory syndrome coronavirus 2 subunit vaccine composed of full-length prefusion stabilized recombinant SARS-CoV-2 spike glycoproteins (S-2P) and aluminum hydroxide adjuvant. In a Phase 1 and 2 studies, (NCT04683484) the vaccine was found to be safe and induce a robust immune response in healthy adult participants.MethodsWe conducted a multicenter, randomized, double-blind, placebo-controlled study to evaluate the safety, immunogenicity, and protective efficacy of the Nanocovax vaccine against Covid-19 in approximately 13,007 volunteers aged 18 years and over. The immunogenicity was assessed based on Anti-S IgG antibody response, surrogate virus neutralization, wild-type SARS-CoV-2 neutralization and the types of helper T-cell response by intracellular staining (ICS) for interferon gamma (IFNg) and interleukin-4 (IL-4). The vaccine efficacy (VE) was calculated basing on serologically confirmed cases of Covid-19.FindingsUp to day 180, incidences of solicited and unsolicited adverse events (AE) were similar between vaccine and placebo groups. 100 serious adverse events (SAE) were observed in both vaccine and placebo groups (out of total 13007 participants). 96 out of these 100 SAEs were determined to be unrelated to the investigational products. 4 SAEs were possibly related, as determined by the Data and Safety Monitoring Board (DSMB) and investigators. Reactogenicity was absent or mild in the majority of participants and of short duration. These findings highlight the excellent safety profile of Nanocovax.Regarding immunogenicity, Nanocovax induced robust IgG and neutralizing antibody responses. Importantly, Anti S-IgG levels and neutralizing antibody titers on day 42 were higher than those of natural infected cases. Nanocovax was found to induce Th2 polarization rather than Th1.Post-hoc analysis showed that the VE against symptomatic disease was 51.5% (95% confidence interval [CI] was [34.4%-64.1%]. VE against severe illness and death were 93.3% [62.2-98.1]. Notably, the dominant strain during the period of this study was Delta variant.InterpretationNanocovax 25 microgram (mcg) was found to be safe with the efficacy against symptomatic infection of Delta variant of 51.5%.FundingResearch was funded by Nanogen Pharmaceutical Biotechnology JSC., and the Ministry of Science and Technology of Vietnam; ClinicalTrials.gov number, NCT04922788.

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Purpose Meningococcal disease is a major global health concern due to its severe and sudden clinical manifestations, devastating long‐term sequelae, and predominance in younger age groups. This study evaluated the safety of a quadrivalent meningococcal polysaccharide diphtheria toxoid conjugate vaccine (MenACWY‐D; Menactra) in participants aged 9 months to 55 years in Vietnam. Methods This was an open‐label, single‐arm study conducted between June and December 2016. Participants received one 0.5‐mL dose of the vaccine, and those aged 9 to 23 months received a second 0.5‐mL dose 3 months later. Participants (or their parents or legal guardians) reported adverse events during the 28 days after each dose. Results The study included 112 participants aged 9 to 23 months and 112 participants aged 2 to 55 years. Of these 224 participants, 100 (44.6%) had one or more solicited reactions within 7 days following any MenACWY‐D dose, mostly injection site pain, lost appetite (in 9 to 23‐month‐olds), and malaise (in 2 to 55‐year‐olds). Most solicited reactions were of mild or moderate intensity and resolved within 3 days. Five participants had unsolicited adverse reactions (ARs), two of which (tonsillitis and febrile convulsion), in 9 to 23‐month‐olds, were considered by the investigator as serious adverse events related to the vaccine. No immediate unsolicited ARs, severe unsolicited nonserious ARs, or unsolicited injection site reactions were reported, and both participants who experienced vaccine‐related serious adverse events recovered. Conclusion Consistent with studies in other countries, MenACWY‐D had an acceptable safety profile in individuals from Vietnam aged 9 months to 55 years (WHO Universal Trial Number: U1111‐1143‐9207).

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