CHMP’s green light is the prerequisite for the European Commission to award conditional marketing authorization for Comirnaty Original/Omicron BA.1 and Spikevax bivalent Original/Omicron BA.1, which are recommended are for use in people aged 12 years and older who have received at least primary vaccination against the virus.

The CHMP-recommended formulations mirror Moderna’s Omicron shot greenlighted by the UK’s health authority Medicines and Healthcare products Regulatory Agency (MHRA) in mid-August, but differ from the bivalent shots developed by the two mRNA vaccine makers that were approved by the US Food and Drug Administration (FDA) at the end of August.

Aimed first at the US market, the latter two target the Omicron 4 and 5 subvariants, which are now prevalent worldwide. The EMA initially had voiced concern about these shots, as they have been tested solely on mice. Full scale human trials are now just beginning.

The vaccines to be rolled out in Europe were tested in small-scale clinical trials with human subjects. CHMP’s opinion on this version of Comirnaty is based on two Pfizer-BioNTech studies. One was conducted with adults over 55 years old who had previously received three doses of Comirnaty (primary vaccination and a booster).

In the Comirnaty study, the immune response was higher after a second booster dose of the original combined with Omicron BA.1 than after a second booster of the original Comirnaty vaccine (as measured by the level of antibodies against Omicron BA.1), the EMA noted.

In addition, the agency said, the immune response to the original strain was comparable for both vaccines. The study involved more than 1,800 people, of whom about 300 received Comirnaty Original/Omicron BA.1 in its final composition. Side effects observed with the adapted vaccine were mild, similar to the original shots.

As the pandemic evolves, the EMA said the EU’s strategy is to have a broad range of adapted vaccines that target different variants so that member states have a plurality of options for when they design their vaccination strategies.

The regulator said it is currently reviewing or will soon review other adapted vaccines incorporating different variants, such as the Omicron subvariants BA.4 and BA.5 being rolled out in the US. The clinical data generated with the original/BA.1 bivalent vaccines CHMP has just recommended will support the evaluation and authorization of further adapted vaccines.

Author: Dede Williams, Freelance Journalist