A few days before Christmas and family reunions around the log, the virus continues to spread widely in France. The bar of 52,000 daily cases (sliding average over seven days) has just been crossed and nearly 16,000 people are hospitalized. If the Omicron variant is not yet the majority – a few hundred cases have been officially identified for the moment in France – it worries the authorities at the highest point.
To fight against its rapid spread, the government has indeed called on the French to go and get massively vaccinated. According to the latest count from the Ministry of Health, more than 19 million of them had received their booster dose on Monday, December 20. This third injection, essential to fight in particular against the severe forms of the disease, seems however, like the first ones, to lose in effectiveness with time, according to several preliminary scientific studies. Franceinfo takes stock of the state of knowledge concerning the efficacy against Omicron of vaccines authorized in the European Union.
Simple vaccination is not effective enough
The speed of transmission and the numerous mutations of the variant identified at the end of November 2021 in South Africa suggest that Omicron escapes the immunity provided by vaccines more than the previous variants.
Regardless of the vaccine injected, scientists agree that two doses are not enough to effectively combat the effects of this new variant of Sars-CoV-2, whether they are mild or severe forms of Covid. -19. A recent study conducted by Imperial London College * even ensures that the level of protection after two doses does not exceed 20%.
Another study conducted by the South African private insurer Discovery Health *, for its part, evaluates the effectiveness of two doses of the Pfizer-BioNTech vaccine at 33% against benign Omicron contaminations (80% against the Delta variant) and at 70% against hospitalization (93% against Delta).
The Institut Pasteur also analyzed the blood of people who had received two doses of the Pfizer vaccine or the AstraZeneca vaccine. Conclusion: “Five months after vaccination, the antibodies present in the blood are no longer able to neutralize Omicron”.
Preliminary data from the United Kingdom point to an effectiveness of around “20% to 40% after the second dose”, confirms in an interview with World, Ugur Sahin, CEO of BioNTech, partner of Pfizer.
Booster dose is more effective
According to several international studies relayed by the New York Times, the third dose therefore appears to be the only solution for effectively combating mild infections and severe forms of the disease with the Omicron variant. But not all vaccines have the same level of effectiveness. The booster shots from the Pfizer-BioNTech and Moderna vaccines, which use messenger RNA technology, offer the best protection against the Omicron variant.
The Pfizer-BioNTech vaccine. British researchers confirm that a third dose of the Pfizer-BioNTech vaccine helps to strengthen the protection and immune response against mild infections of the Omicron variant, with an estimated effectiveness of 70% for people who had initially received the AstraZeneca vaccine and ‘approximately 75% for those who received Pfizer *.
The Institut Pasteur is also validating the efficacy of a third dose of the Pfizer-BioNTech vaccine against Omicron. “A third booster dose with Pfizer vaccine, or the injection of one dose of vaccine in people with a previous infection, greatly increases antibody levels, to a level sufficient to neutralize Omicron.”, explain the French researchers.
Moderna’s vaccine. The pharmaceutical company announced in a statement on Dec. 20 * that the currently authorized booster dose of 50 micrograms increased the antibody level by 37 times and that a booster dose of 100 micrograms was even more potent, increasing the levels of antibody about 83 times over the levels obtained with the first two doses.
The Janssen vaccine from Johnson & Johnson. It is the only one that only works with a single dose to provide a complete regimen. It is also the last to have received the green light from the European Medicines Agency (EMA) to be used as a booster dose, even if the French authorities still recommend, after a first dose of Janssen vaccine, a dose of vaccine to Messenger RNA.
The EMA recommendation “follows data showing that a booster dose of the Janssen Covid-19 vaccine given at least two months after the first dose in adults resulted in an increase in antibodies against Sars-CoV-2”, said last week the institution in a press release (link in English). However, no figures on the effectiveness of this vaccine against Omicron have been revealed.
Johnson & Johnson, for their part “be in the process of evaluating the effectiveness of its vaccine against Covid-19 against variants” and also specified to be “working on a vaccine more specific to Omicron, which it will develop as needed”.
Doubt about the duration of protection
Although the third dose is essential for the control of infections caused by the Omicron variant, the duration of protection conferred by the booster is uncertain. For researchers at the Institut Pasteur, people who have received a third dose of the Pfizer-BioNTech vaccine remain protected against Omicron one month after the injection. “However, it takes 5 to 31 times more antibodies to neutralize Omicron, compared to Delta”, they warn. “It is now necessary to study the duration of protection of the booster dose. The vaccines therefore probably lose a strong efficacy against the acquisition of the virus but should continue to protect against the severe forms”, specifies Olivier Schwartz, one of the main authors of the Institut Pasteur study.
According to Ugur Sahin, CEO of BioNTech, “there will be a loss of efficacy against Omicron over time, it is very likely, but we still have to measure the speed”, he admits, ensuring that his laboratory is currently working on the design and if possible on delivery in March of “vaccines suitable for Omicron, subject to regulatory approval.”
So should we consider specific vaccines to fight in the future against each variant and in particular Omicron? Maybe but “You should absolutely not wait for a possible vaccine adapted to the Omicron variant rather than carrying out its booster dose”, insists Alain Fischer, chairman of the Orientation Council for the vaccine strategy, in The Parisian.
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