Phase 2 trial evaluates the safety and immunogenicity of two doses of the SARS-CoV-2 vaccine MVC-COV1901 in adolescents

A recent study posted to the medRxiv* preprint server evaluated the safety and immunogenicity of a coronavirus disease 2019 (COVID-19) vaccine in a phase II trial.

Study: Safety and immunogenicity of SARS-CoV-2 vaccine MVC-COV1901 in adolescents in Taiwan: A double-blind, randomized, placebo-controlled phase 2 trial. Image Credit: Ken stocker/Shutterstock


The natural evolution rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is too high to permit the extinction of extant variants before the emergence of newer variants. Moreover, there are concerns that the COVID-19 pandemic might become endemic. Therefore, the currently available treatments should be redesigned regularly to ensure that newer variants are suppressed optimally.

Vaccination against the virus is the most effective strategy to prevent severe infection, and globally more than 10.7 billion vaccine doses have been administered so far. Despite the extensive immunization drive, COVID-19 infections have lately surged to record high levels across all regions after the SARS-CoV-2 Omicron variant emerged.

The MVC-COV1901 vaccine is a protein subunit vaccine of S-2P, the stable prefusion form of SARS-CoV-2 spike (S) protein. This vaccine has been approved for emergency use in Taiwan for people aged 18 years or above; however, its safety and immunogenicity among those < 18 years is not investigated. It is crucial to evaluate these parameters in the mentioned age group to ensure every age group can become eligible for a COVID-19 vaccine and be protected against infection.

The study

In the present study, researchers conducted a phase II trial of the two-dose MVC-COV1901 vaccine in adolescents aged 12 – 17 years. The trial is a prospective, multi-center, double-blind study designed to investigate the immunogenicity and safety of the MVC-COV1901 vaccine. Participants were eligible if they were 12 – 17 years at randomization, without any travel history in the past 14 days, and not traveling overseas throughout the study period. They were randomized in a 6:1 ratio to receive MVC-COV1901 or a placebo (saline).

Participants received two intramuscular injections of MVC-COV1901 or placebo doses 28 days apart. The MVC-COV1901 vaccine comprised S-2P and adjuvants (CpG 1018 and aluminum hydroxide) for a final volume of half a milliliter. Specimens were collected from the participants at six time points on days 0, 1, 28, 29, 57, 119, and 209.

The participants’ vital signs were assessed pre-and post-vaccine administration; they were observed for any adverse events 30 minutes after each injection. Solicited adverse events (AE), unsolicited AEs, vaccine-associated enhanced disease (VAED), AEs of special interest (AESI), and severe AEs were monitored for safety analysis. Live virus neutralization assay and anti-S protein IgG antibodies were determined for evaluating immunogenicity profiles.


The authors recruited 405 participants between July 21st – December 22nd, 2021, and excluded six ineligible candidates. After randomization, 341 candidates received the MVC-COV1901 vaccine, and 58 were placebo controls. Immunogenicity parameters of the adolescents were compared with that of adults aged 20 – 30 years. Researchers observed mild solicited AEs and identified pain/tenderness as the only significant local AE. Fatigue/malaise was the most common systemic AE. Over 26% of subjects experienced unsolicited AEs, and there were no cases of AESI, VAED, SAE, or deaths.

The primary immunogenicity endpoint was assessed on day 57 by comparing geometric mean titers (GMT) and seroconversion rate (SCR) between adults and adolescents. The GMT of adolescents was 648.5 international units (IU)/ml compared to 559.5 IU/ml in adults. A GMT ratio of 1.16 was calculated, indicating non-inferior immunogenicity of the vaccine in adolescents relative to adults.

Next, secondary immunogenicity endpoints were evaluated; the baseline neutralizing antibody (nAb) and IgG levels were similar during their second visit (day 0) between the vaccinated subjects and placebo controls. Two vaccinations increased the GMT to 648.5 IU/ml. At the same time, it remained at the baseline levels in the placebo group, resulting in a ratio of 115.2 between the vaccine and placebo groups’ GMT levels. During the fourth visit of the subjects, the GMT of vaccinated individuals was 136 IU/ml, which increased to 1632 IU/ml by their sixth visit.


The current study investigated the safety and immunogenicity profiles of two doses of the MVC-COV1901 vaccine among adolescents aged 12 – 17 years. Local solicited AEs were more common in the vaccinated adolescents than placebo-controlled subjects.

Overall, the AEs observed in the adolescents were similar to that reported in adults, indicating a favorable safety profile for adolescents. Notably, nAb and IgG titers were more significant in adolescents than adults. It is noteworthy that since the study is a phase II trial, the vaccine’s efficacy among adolescents is yet to be determined.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
  • Liu, L. et al. (2022) "Safety and immunogenicity of SARS-CoV-2 vaccine MVC-COV1901 in adolescents in Taiwan: A double-blind, randomized, placebo-controlled phase 2 trial". medRxiv. doi: 10.1101/2022.03.14.22272325.

Posted in: Medical Science News | Medical Research News | Disease/Infection News

Tags: Adolescents, Antibodies, Antibody, Assay, Coronavirus, Coronavirus Disease COVID-19, covid-19, CpG, Efficacy, Evolution, Fatigue, Immunization, Omicron, Pain, Pandemic, Placebo, Protein, Respiratory, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Syndrome, Vaccine, Virus

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Tarun Sai Lomte

Tarun is a writer based in Hyderabad, India. He has a Master’s degree in Biotechnology from the University of Hyderabad and is enthusiastic about scientific research. He enjoys reading research papers and literature reviews and is passionate about writing.

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