Name: Spikevax (elasomeran, Moderna COVID-19 Vaccine, mRNA-1273)

Type: Genetic vaccine (messenger RNA/mRNA)

Developer: ModernaTX, Inc.

Recommended schedule: 2 doses (4-6 weeks apart)

Doses for Australia: Contract for 25 million doses from late 2021 (10 million doses of the current formulation, as well as an additional 15 million doses of variant-specific versions)

Storage: Must be stored at temperatures of -50°C to -15°C. Unopened vials can be thawed and stored or transported in refrigerators at temperatures of 2°C to 8°C for up to 30 days. Opened vials can be stored between  2°C to 25°C for 12 hours before they must be discarded.  Once thawed, Spikevax (elasomeran) cannot be refrozen.

Preparation and injection: Each multi-dose vial contains either 11 or 15 doses of 0.5ml of vaccine. The vaccine must be thawed before injection and does not require reconstitution. It is administered via intramuscular (IM) injection.


Spikevax (elasomeran) utilises an mRNA platform which codes for a stabilised version of the SARS-CoV-2 spike protein. On 24 June 2021, the TGA granted provisional determination for people aged > 12 years. On 9th August 2021, Spikevax (elasomeran) was granted provisional registration by the TGA for people aged > 18 years for the active immunisation to prevent COVID-19 disease.


Pre-clinical trials were conducted in mice which showed that two doses of the vaccine protected the mice from infection with the SARS-CoV-2 virus with no virus detected in the lower respiratory tract and nose following a challenge with the SARS-CoV-2 virus. These results indicated the vaccine may reduce both infection and transmission in humans.

The US phase 1 trial included participants aged 18-55 years old who received two injections of Spikevax (elasomeran) 28 days apart at doses of 25 μg, 100 μg or 250 μg. The vaccine elicited a strong immune response without any severe adverse events and the trial supported the selection of the 100 μg  dose for advancement to Phase 2/3 trials.

Safety profile

During clinical trials, symptoms following immunisation were generally mild to moderate and short-term. Local and systemic reactions were more common after the second dose and in the younger age group (18-64 years).

Local reactions included pain (86-90%) and redness (3-9%) at the injection site and axillary (armpit) swelling/tenderness (11-16%). The average onset of local reactions was 1 day after either dose, with an average duration of 2-3 days.

Systemic reactions (including fatigue, headache,  muscle ache, joint pain, chills, nausea and vomiting) were more common after the second dose (82%) compared to the first dose (57%).  Fever was more common following the second dose (17%). The average onset of local reactions was 1-2 days after either dose, with an average duration of 2 days. The incidence of serious adverse events was very low (1%) and similar in both the vaccine and placebo groups.

Vaccine efficacy

phase 3 trial enrolling 30,420 volunteers aged ≥18 years, assigned participants to receive either the vaccine or placebo as two intramuscular injections 28 days apart. Spikevax (elasomeran) showed overall efficacy of 94.1% for preventing COVID-19 illness, and 100% efficacy for preventing severe disease. Vaccine efficacy was consistent across subgroups stratified by age group (18 to < 65 years of age, ≥ 65 years, presence of risk for severe COVID-19 disease, sex, race and ethnic groups).

Further studies

Paediatric clinical trials

Children were not included in the initial Moderna COVID-19 vaccine clinical trials due to the decrease in severity of symptoms experienced by children infected with SARS-CoV-2 compared with infected adults. Various clinical trials are currently underway to determine the safety and efficacy of Spikevax (elasomeran) in the paediatric population.

For further information, refer to MVEC: COVID-19 vaccination in children.

Mixed vaccine schedules

Clinical trials are currently underway to evaluate the immunogenicity and reactogenicity of combining Spikevax (elasomeran) with different COVID-19 vaccine brands to complete a COVID-19 vaccine course.

For further information refer to MVEC: COVID-19 mixed vaccine schedules.

Post-licensure surveillance


A true vaccine allergy (anaphylaxis) is a rare side effect occurring for all vaccines at a rate of approximately 1 case per million vaccine doses administered. Post-licensure surveillance of Spikevax (elasomeran) in the US has shown that it has a slightly higher rate of anaphylaxis with approximately 2.5 cases per million. Most cases (89%) occurred within 30 minutes of vaccination and 26% had a history of prior anaphylaxis.


A small number of cases of myocarditis and pericarditis have been reported in individuals vaccinated with COVID-19 mRNA vaccines (eg. Comirnaty™ and Spikevax (elasomeran)). Reports have predominantly involved adolescents and young adults, more commonly males, after the second dose of vaccine. Symptom onset has typically been seen within 4 days of vaccination.


Authors: Rachael McGuire, (MVEC Education Nurse Coordinator), Francesca Machingaifa (MVEC Education Nurse Coordinator) and Davina Buntsma (MVEC Immunisation Fellow)

Reviewed by: Rachael McGuire (MVEC Education Nurse Coordinator)

Date: 10 August 2021

Materials in this section are updated as new information and vaccines become available. The Melbourne Vaccine Education Centre (MVEC) staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.