Approved indication: prevention of COVID-19
Spikevax bivalent original/Omicron BA.4-5 (Moderna)
prefilled syringes containing doses of 25+25 micrograms/0.5 mL suspension for injection

The COVID-19 pandemic stimulated the rapid development of vaccines against the SARS-CoV-2 ancestral strain. However, variants of the virus soon appeared and the Omicron variant became the most prevalent in Australia. Subsequently, several subvariants of the Omicron variant have emerged that have a greater potential to escape vaccine-elicited immunity. The composition of the vaccines therefore needed to be adapted to counter these subvariants.

Elasomeran (Spikevax [Moderna]) was one of the early messenger RNA (mRNA) vaccines. Subsequently, a bivalent form of the vaccine was developed containing elasomeran+imelasomeran with the aim of improving protection against the Omicron BA.1 subvariant. To improve protection against the Omicron BA.4-5 subvariants, elasomeran has now been combined with davesomeran, an mRNA vaccine that encodes the viral spike protein of the Omicron BA.4-5 subvariants. Like elasomeran, davesomeran is formulated in lipid nanoparticles to enable it to enter cells.

The combination of elasomeran+davesomeran has been provisionally approved as a booster dose for people 12 years and older who have had at least a primary course of vaccination. The intramuscular dose of 25+25 micrograms is given at least 3 months after the primary course or a previous booster. The product information does not address the need for dosage adjustment in patients with liver or kidney impairment.

The trials of elasomeran+davesomeran are ongoing. In data submitted to the Therapeutic Goods Administration, 511 people were given the combination as a booster. They were compared with 376 people who were given a booster of elasomeran alone. Titres of Omicron BA.4-5 neutralising antibodies increased in both groups 28 days after the booster was injected. The response to elasomeran+davesomeran met the criteria for statistical superiority compared to elasomeran alone for antibodies against the Omicron BA.4-5 subvariants, and for statistical noninferiority for antibodies against the ancestral strain.

The short-term adverse effects of elasomeran+davesomeran are similar to those of elasomeran. They include injection-site reactions, fatigue, headache, myalgia, nausea and vomiting, and lymphadenopathy. Health professionals should be aware that there may be an increased risk of myocarditis and pericarditis, particularly in males younger than 40 years of age.1

While elasomeran+davesomeran induces a superior antibody response, data are limited on whether this translates into better clinical effectiveness against infections with the Omicron BA.4-5 subvariants. Two observational studies that compared BA.4-5 bivalent boosters with monovalent boosters found bivalent boosters offered greater protection against symptomatic infection, hospitalisation and death.2,3

In the USA, monovalent boosters are no longer recommended, and the Australian Technical Advisory Group on Immunisation has expressed a preference for use of mRNA bivalent vaccines as boosters for those age groups in whom they are approved.4

At present, the duration of protection following a booster of elasomeran+davesomeran is unknown.

🅃 manufacturer provided the AusPAR and/or the product information. The Transparency Score is explained in New drugs: transparency, Vol 37 No 1, Aust Prescr 2014;37:27.

At the time the comment was prepared, information about this drug was available on the websites of the Food and Drug Administration in the USA, the European Medicines Agency and the Therapeutic Goods Administration.


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The new drug commentaries in Australian Prescriber are prepared by the editors and reviewed by the Editorial Executive Committee. Some of the views expressed on newly approved products should be regarded as preliminary, as there may be limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is mportant that more detailed information is obtained from the manufacturer’s approved product information, a drug information centre or some other appropriate source.

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