Interim safety and immunogenicity of COVID-19 omicron BA.1 variant-containing vaccine in children in the USA: an open-label non-randomised phase 3 trial.

BACKGROUND: Variant-containing mRNA vaccines for COVID-19 to broaden protection against SARS-CoV-2 variants are recommended based on findings in adults. We report interim safety and immunogenicity of an omicron BA.1 variant-containing (mRNA-1273.214) primary vaccination series and booster dose in paediatric populations. METHODS: This open-label, two-part, non-randomised phase 3 trial enrolled participants aged 6 months to 5 years at 24 US study sites. Eligible participants were generally healthy or had stable chronic conditions, without known SARS-CoV-2 infection in the previous 90 days. Individuals who were acutely ill or febrile 1 day before or at the screening visit or those who previously received other COVID-19 vaccines (except mRNA-1273 for part 2) were excluded. In part 1, SARS-CoV-2-vaccine-naive participants received two-dose mRNA-1273.214 (25 µg; omicron BA.1 and ancestral Wuhan-Hu-1 mRNA) primary series. In part 2, participants who previously completed the two-dose mRNA-1273 (25 µg) primary series in KidCOVE (NCT04796896) received a mRNA-1273.214 (10 µg) booster dose. Primary study outcomes were safety and reactogenicity of the mRNA-1273.214 primary series (part 1) or booster dose (part 2) as well as the inferred effectiveness of mRNA-1273.214 based on immune responses against ancestral SARS-CoV-2 (D614G) and omicron BA.1 variant at 28 days post-primary series (part 1) or post-booster dose (part 2). The safety set included participants who received at least one dose of the study vaccine; the immunogenicity set included those who provided immunogenicity samples. Interim safety and immunogenicity are summarised in this analysis as of the data cutoff date (Dec 5, 2022). This trial is registered with ClinicalTrials.gov, NCT05436834. FINDINGS: Between June 21, 2022, and Dec 5, 2022, 179 participants received one or more doses of mRNA-1273.214 primary series (part 1) and 539 received a mRNA-1273.214 booster dose (part 2). The safety profile within 28 days after either dose of the mRNA-1273.214 primary series and the booster dose was consistent with that of the mRNA-1273 primary series in this age group, with no new safety concerns or vaccine-related serious adverse events observed. At 28 days after primary series dose 2 and the booster dose, both mRNA-1273.214 primary series (day 57, including all participants with or without evidence of prior SARS-CoV-2 infection at baseline) and booster (day 29, including participants without evidence of prior SARS-CoV-2 infection at baseline) elicited responses that were superior against omicron-BA.1 (geometric mean ratio part 1: 25·4 [95% CI 20·1-32·1] and part 2: 12·5 [11·0-14·3]) and non-inferior against D614G (part 1: 0·8 [0·7-1·0] and part 2: 3·1 [2·8-3·5]), compared with neutralising antibody responses induced by the mRNA-1273 primary series (in a historical comparator group). INTERPRETATION: mRNA-1273.214 was immunogenic against BA.1 and D614G in children aged 6 months to 5 years, with a comparable safety profile to mRNA-1273, when given as a two-dose primary series or a booster dose. These results are aligned with the US Centers for Disease Control and Prevention recommendations for the use of variant-containing vaccines for continued protection against the emerging variants of SARS-CoV-2. FUNDING: Moderna.

Evaluation of mRNA-1273 Vaccine in Children 6 Months to 5 Years of Age.

BACKGROUND: The safety, reactogenicity, immunogenicity, and efficacy of the mRNA-1273 coronavirus disease 2019 (Covid-19) vaccine in young children are unknown. METHODS: Part 1 of this ongoing phase 2-3 trial was open label for dose selection; part 2 was an observer-blinded, placebo-controlled evaluation of the selected dose. In part 2, we randomly assigned young children (6 months to 5 years of age) in a 3:1 ratio to receive two 25-µg injections of mRNA-1273 or placebo, administered 28 days apart. The primary objectives were to evaluate the safety and reactogenicity of the vaccine and to determine whether the immune response in these children was noninferior to that in young adults (18 to 25 years of age) in a related phase 3 trial. Secondary objectives were to determine the incidences of Covid-19 and severe acute respiratory syndrome coronavirus 2 infection after administration of mRNA-1273 or placebo. RESULTS: On the basis of safety and immunogenicity results in part 1 of the trial, the 25-µg dose was evaluated in part 2. In part 2, 3040 children 2 to 5 years of age and 1762 children 6 to 23 months of age were randomly assigned to receive two 25-µg injections of mRNA-1273; 1008 children 2 to 5 years of age and 593 children 6 to 23 months of age were randomly assigned to receive placebo. The median duration of follow-up after the second injection was 71 days in the 2-to-5-year-old cohort and 68 days in the 6-to-23-month-old cohort. Adverse events were mainly low-grade and transient, and no new safety concerns were identified. At day 57, neutralizing antibody geometric mean concentrations were 1410 (95% confidence interval [CI], 1272 to 1563) among 2-to-5-year-olds and 1781 (95% CI, 1616 to 1962) among 6-to-23-month-olds, as compared with 1391 (95% CI, 1263 to 1531) among young adults, who had received 100-µg injections of mRNA-1273, findings that met the noninferiority criteria for immune responses for both age cohorts. The estimated vaccine efficacy against Covid-19 was 36.8% (95% CI, 12.5 to 54.0) among 2-to-5-year-olds and 50.6% (95% CI, 21.4 to 68.6) among 6-to-23-month-olds, at a time when B.1.1.529 (omicron) was the predominant circulating variant. CONCLUSIONS: Two 25-µg doses of the mRNA-1273 vaccine were found to be safe in children 6 months to 5 years of age and elicited immune responses that were noninferior to those in young adults. (Funded by the Biomedical Advanced Research and Development Authority and National Institute of Allergy and Infectious Diseases; KidCOVE ClinicalTrials.gov number, NCT04796896.).

Evaluation of mRNA-1273 Covid-19 Vaccine in Children 6 to 11 Years of Age.

BACKGROUND: Vaccination of children to prevent coronavirus disease 2019 (Covid-19) is an urgent public health need. The safety, immunogenicity, and efficacy of the mRNA-1273 vaccine in children 6 to 11 years of age are unknown. METHODS: Part 1 of this ongoing phase 2-3 trial was open label for dose selection; part 2 was an observer-blinded, placebo-controlled expansion evaluation of the selected dose. In part 2, we randomly assigned children (6 to 11 years of age) in a 3:1 ratio to receive two injections of mRNA-1273 (50 µg each) or placebo, administered 28 days apart. The primary objectives were evaluation of the safety of the vaccine in children and the noninferiority of the immune response in these children to that in young adults (18 to 25 years of age) in a related phase 3 trial. Secondary objectives included determination of the incidences of confirmed Covid-19 and severe acute respiratory syndrome coronavirus 2 infection, regardless of symptoms. Interim analysis results are reported. RESULTS: In part 1 of the trial, 751 children received 50-µg or 100-µg injections of the mRNA-1273 vaccine, and on the basis of safety and immunogenicity results, the 50-µg dose level was selected for part 2. In part 2 of the trial, 4016 children were randomly assigned to receive two injections of mRNA-1273 (50 µg each) or placebo and were followed for a median of 82 days (interquartile range, 14 to 94) after the first injection. This dose level was associated with mainly low-grade, transient adverse events, most commonly injection-site pain, headache, and fatigue. No vaccine-related serious adverse events, multisystem inflammatory syndrome in children, myocarditis, or pericarditis were reported as of the data-cutoff date. One month after the second injection (day 57), the neutralizing antibody titer in children who received mRNA-1273 at a 50-µg level was 1610 (95% confidence interval [CI], 1457 to 1780), as compared with 1300 (95% CI, 1171 to 1443) at the 100-µg level in young adults, with serologic responses in at least 99.0% of the participants in both age groups, findings that met the prespecified noninferiority success criterion. Estimated vaccine efficacy was 88.0% (95% CI, 70.0 to 95.8) against Covid-19 occurring 14 days or more after the first injection, at a time when B.1.617.2 (delta) was the dominant circulating variant. CONCLUSIONS: Two 50-µg doses of the mRNA-1273 vaccine were found to be safe and effective in inducing immune responses and preventing Covid-19 in children 6 to 11 years of age; these responses were noninferior to those in young adults. (Funded by the Biomedical Advanced Research and Development Authority and the National Institute of Allergy and Infectious Diseases; KidCOVE ClinicalTrials.gov number, NCT04796896.).