The arms race against Covid-19 is taking a new step. The European Medicines Agency (EMA) gave its agreement on Thursday 1is September, for the use of two latest generation vaccines against the SARS-CoV-2 virus, produced by the companies Moderna and Pfizer-BioNTech. According to the EMA, they can be given as a booster in people over 12 who have already received a primary vaccination against Covid-19. So far, only the United Kingdom and Switzerland have approved one of these vaccines, that of Moderna.
Will they be, as hoped, more effective shields against the epidemic? These products, which use the same messenger RNA technology as the vaccines already in use, have been designed to be more suitable for the strains of the virus currently circulating, i.e. one of the versions of Omicron , the subvariant BA.1. Vaccines targeting BA.4 and BA.5 are in the process of being licensed in Europe. In addition, they continue to rely on the immunity conferred by the ancestral strain of the SARS-CoV-2 virus, the very first to have been identified in Wuhan at the end of 2019. Building on the achievements while adapting to the he evolution of the virus is the gamble of these so-called “bivalent” vaccines.
Since the SARS-CoV-2 appeared, it has not stopped changing clothes, new variants and sub-variants appearing over its mutations. With each new wave, the virus has thus weakened the capacities of our immune cells, “learned” by vaccination or by a previous infection. The vaccines used so far have certainly been proven to prevent serious forms of Covid-19. But their effectiveness against the transmission of the virus and against the infections themselves, imperfect from the outset, dwindles over the weeks. So what can we expect from these new generations of updated vaccines? Overview.
What do we know about the effectiveness of these bivalent vaccines?
Following separate applications for approval by Pfizer and Moderna in July, the EMA used an accelerated assessment procedure: theimmunobridging. Clearly, it is a question of measuring, in people vaccinated with one of these new preparations, the production of antibodies in the blood and comparing it with the response induced by current vaccines, whose effectiveness has already been proven.
In this procedure, we therefore do not wait to know the results of the protection conferred against the risk of infection or serious forms. This would have required following the vaccinated people for many months to compare, in the vaccinated group and in the control group, the rates of people who will have been infected or who will have had serious forms. Results ? In its press release, the EMA justifies that the two vaccines “were more effective in eliciting immune responses against the BA.1 subvariant than the original vaccines”. All with comparable side effects, “generally mild and short-lived”.
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