Covid-19: at the dawn of the eighth wave, HAS approves three vaccines adapted to Omicron

The High Health Authority gives the green light, this Tuesday, September 20, to three anti-Covid vaccines adapted to Omicron for a new booster vaccination campaign planned for the fall and coupled with that against the flu. This new booster dose will be recommended to people at risk of a severe form, to those around them and to caregivers. The HAS recommends “indifferently one of the three bivalent vaccines” – two developed by Pfizer / BioNTech, the third by Moderna – recently validated by the European Medicines Agency. “Based on the available data and in an epidemic context marked by the majority circulation of the BA.5 sub-variant”, the HAS recommends using “preferably” one of these vaccines, all with messenger RNA, for a new fall booster dose. This recommendation applies regardless of the anti-Covid vaccine initially administered to the person.

“Like seasonal influenza vaccines, updated each year to take into account the viruses that are most likely to circulate during the winter, bivalent mRNA vaccines are not new vaccines but vaccines adapted to the strains circulating”, underlines the HAS in its press release. These are the vaccines from Moderna and Pfizer/BioNTech targeting the original strain of the virus and the BA.1 variant of Omicron, and the vaccine from Pfizer/BioNTech targeting the original strain and the BA subvariants .4 and BA.5 from Omicron.

The HAS is also maintaining its recommendation to combine the booster vaccination campaign against Covid-19 with that of vaccination against influenza, which will start on October 18. A concomitant injection or the same day of the two vaccines is possible, she recalls. “In the immediate future and because the number of cases of infections has started to rise again for a few days”, this health authority recommends not to postpone the second booster dose in people over 60 and under 60. at risk of a severe form who have not received it within the recommended time frame.

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The fear of an eighth wave

Is a new wave of Covid-19 setting in? For a few days, doubt has been allowed. With more than 27,000 new cases per day between September 9 and 16, contaminations are up 57% compared to the previous week. Sign of a real increase in the virus on the territory, the positivity rate also climbs, going from 16 to 19 (+ 18%) between September 9 and 16. “It is not an accidental rise, but a real trend spanning several days and which potentially marks the start of an eighth wave”, estimates Pascal Crépey, epidemiologist and professor of public health at the Ecole des Hautes Etudes. in public health.

How to explain this recovery? According to the count carried out by Public Health France, the dynamic remains attributable to the sub-variant of Omicron BA.5, which represents more than 95% of samples in France. It is still difficult to know the extent of this new wave, but the injection of a second booster dose (a fourth dose) is recommended by the health authorities for all people over 60 and for “adults under 60 years old identified as being at risk of a serious form of Covid19, to pregnant women and to people living in the entourage or in regular contact with immunocompromised or vulnerable people”, recalls the High Authority for Health (HAS).

Bivalent vaccines (almost) all authorized in France

In this regard, there is a novelty: the new generation Covid-19 vaccines called “bivalent”. These messenger RNA vaccines, produced by Pfizer and Moderna laboratories, target both the historical strain of the virus and the Omicron variant. There are two versions: one fights the original virus and the Omicron BA.1 subvariant; the other against the original virus and the Omicron BA.4 and BA.5 subvariants. In the United States, the Food and Drug Administration (FDA, the American drug agency) has authorized the bivalent BA.4/BA.5 vaccines from Pfizer and Moderna. In Europe, the European Medicines Agency (EMA) has authorized the bivalent BA.1 vaccines from Pfizer and Moderna and has recently authorized the BA.4/BA.5 from Pfizer, but not yet from Moderna.

Inevitably, new questions arise. Are bivalent vaccines really more effective than historical vaccines, and should we wait until they are on the market to be injected with a fourth dose? Admittedly, historical vaccines are less effective against Omicron and its subvariants, exhibiting escape capabilities, than against previous strains. They do not prevent, or very little, the infection and the transmission of the virus. On the other hand, the protection they grant against serious forms of Omicron remains “very effective”, with “effectiveness on hospitalizations and on the transition to critical care of 80 and 92%”, assures the French Society of Pharmacology and of therapy. “Scientific data indicate that booster doses provide good protection – through the production of neutralizing antibodies – against severe forms of Omicron and its subvariants, but this protection decreases after three months in those under 65 years of age. and even earlier (after a month and a half) in the oldest and the immunocompromised”, specifies Morgane Bomsel, virologist and CNRS researcher at the Cochin Institute.

As for bivalent vaccines, there are certain certainties, but also questions. The two BA.1 and BA.4/BA.5 versions have passed the safety tests: they do not present any toxicity for humans. They are also believed to allow our immune system to produce more effective antibodies against these Omicron BA.1 and BA.4/BA.5 subvariants. At least in theory, because in practice the data is lacking. The Pfizer and Moderna laboratories did not have the time to conduct clinical efficacy trials. “The bivalent BA.1 formulation currently approved is mainly based on laboratory tests, using neutralizing antibodies in human serum; and the bivalent BA.4-BA.5 has been approved in the United States (where it is widely distributed ) on the sole basis of tests carried out in rodents”, explains Antoine Flahault, epidemiologist, director of the Institute of Global Health and professor at the Faculty of Medicine of Geneva.

Historic, bivalent vaccine, how effective?

“The laboratories claim that a booster with a bivalent vaccine leads to the production of more effective antibodies than with a booster dose of a ‘historic’ vaccine, but they do not indicate whether this is 10 or 30 times more effective” , confirms Morgane Bomsel. And when the choice between the bivalent BA.1 vaccine and the BA.4/BA.5 arises, which should be chosen? BA.1 was developed a little earlier, and scientists have more data about it.

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Nevertheless, the logic would like that BA.4/BA.5 is preferred, since this last sub-variant is very largely predominant. “The BA.1 bivalent already seems a little outdated to me today and might not appear much more effective than the original monovalent”, notes Antoine Flahault. As for BA.4/BA.5, the specialist believes that it is necessary to wait for the data from “real-life experience conducted in the United States”. According to him, individuals who have not been vaccinated or infected for more than three months should therefore not wait for the bivalent vaccines to be injected with a fourth dose. “We know today that people who have received four doses of monovalent vaccine are less often hospitalized than those who have received three, while for the bivalent vaccine we do not yet have these data, he notes. fourth dose is therefore highly recommended, and without delay, for all adults eligible for vaccination, and in priority to people at risk of severe forms.

Victor Garcia and Valentin Ehkirch