In Week 52 (December 27 to January 2), a very sharp increase in SARS-CoV-2 transmission was observed across the country (+129%) due to the variant’s rapid spread. The incidence rate reached 1,908 cases per 100,000 inhabitants, meaning nearly 2% of the population tested positive in week 52. The adjusted incidence rate at least doubled in all age groups. The sharpest increases in the incidence rate were observed in the overseas territories, particularly in Mayotte (870, +664%) and Guadeloupe (1,218, +486%). New hospitalizations were on the rise in nearly all regions, most notably among those under 40, and particularly among those under 10. As of January 4, 77.2% of the total population had received a full primary vaccination series. Among those aged 18 and older, 48.4% had received a booster dose (72.9% among those aged 65 and older). Given the very high rate of spread of the Omicron variant (74% of screening tests now indicate this variant), strict adherence to all preventive measures—including mask-wearing and reducing contact, as well as frequent ventilation of enclosed spaces and working from home—is more necessary than ever to try to slow the number of infections and protect the most vulnerable. Stepping up vaccination efforts, including booster shots as early as three months after the initial dose, and following all recommended measures in the event of symptoms, a positive test, or exposure to a high-risk contact, are essential to limit the impact on the healthcare system.

More than 168,000 cases diagnosed on average each day and a doubling of the incidence rate

Nationally, the incidence rate adjusted for the effect of the holiday (January 1) rose sharply in week 52, reaching 1,908 cases per 100,000 inhabitants (vs. 835 in week 51, a 129% increase). On average, more than 168,000 cases were diagnosed each day. The effective reproduction number stood at 1.61 on January 1 (vs. 1.22 on December 25), indicating a marked acceleration in viral circulation. The adjusted incidence rate at least doubled in all age groups. It tripled among those aged 70–79 (+207%) and 80–89 (+212%). It stood at 3,606 (+103%) among those aged 20–29 and 2,905 (+112%) among those aged 30–39. The adjusted testing rate increased (+17%) across all age groups, with the exception of those aged 0–9, where it declined again, in line with school holidays (-4%). The test positivity rate rose sharply and reached its highest level since the start of the epidemic (17.1%, +8.4 percentage points).

In mainland France, the adjusted incidence rate rose across the entire country, reaching 3,036 (+115%) in Île-de-France, 2,444 in Corsica (+135%), and 2,072 (+106%) in Auvergne-Rhône-Alpes. In the overseas territories, the adjusted incidence rate rose very sharply in all regions. It reached 1,281 (+92%) in Réunion and 1,218 (+486%) in Guadeloupe. Mayotte saw the sharpest increase in the incidence rate (870, +664%) and in new hospitalizations.

Increase in new hospitalizations and stabilization of critical care admissions at high levels

The number of new hospitalizations increased (+18%) while critical care admissions remained stable (-3%). As of January 4, 20,252 COVID-19 patients were hospitalized, including 3,678 in critical care. Among all COVID-19 patients, the proportion of patients hospitalized for COVID-19 treatment has remained stable in recent weeks (84% in Week 52 vs. 86% in Week 51 for hospitalizations and 94% vs. 95% for critical care). The number of deaths increased by 6%, totaling 1,275 deaths, including 59 in long-term care facilities.

In mainland France, the number of new hospitalizations increased in nearly all regions. In the overseas territories, Mayotte saw the sharpest rise in new hospitalizations. New hospital admissions were also on the rise in French Guiana and Réunion.

Omicron: What do we know so far about its impact on the population?

Preliminary analyses from the United Kingdom, Canada, the United States, and Israel suggest a reduced risk of hospitalization for Omicron compared to other variants (by 56% to 81%), but these data should be interpreted with caution because the majority of infection cases are still observed in a younger population, which is therefore at lower risk.

In France, data from the OSCOUR® network show a declining hospitalization rate following visits to the emergency department for suspected COVID-19 over the past two weeks (36% in Week 52 vs. 50% in Week 50), while the hospitalization rate following visits for all causes has remained stable. These findings suggest that cases presenting to the emergency department with suspected COVID-19 have been less severe over the past two weeks (during which the Omicron variant became the dominant strain). This preliminary interpretation should be treated with caution.

74% of screened tests are compatible with Omicron

The screening strategy implemented in France aims to proactively detect mutations that affect transmissibility, severity, or immune escape. Certain mutation profiles raise suspicion of the presence of specific variants. The screening strategy is regularly updated to closely monitor circulating viruses. Since December 20, 2021, this strategy has been looking for the E484K mutation (coded as A in the SI-DEP database) and the L452R mutation (coded as C), as well as a panel of mutations more specific to Omicron (coded as D).

Since January 6, 2022, Santé publique France has made five new indicators available as open data on a 7-day rolling basis. They are available daily on the Géodes platform and the data.gouv.fr website and are broken down at the national and regional levels. The InfoCovidFrance dashboard is also evolving.

• More information - Circulation of SARS-CoV-2 variants

In week 52, the proportion of A0C0 samples (compatible with Omicron because they do not carry the E484K and L452R mutations) increased significantly (74%, or 259,794 results, vs. 42% in week 51), with regional disparities. In mainland France, the proportion of A0C0 ranged from 51% in Provence-Alpes-Côte d’Azur to 90% in Île-de-France. The proportion of A0C0 was also rising in Guadeloupe, Martinique, and Réunion, although it remained lower than in mainland France. Conversely, the proportion of screened positive samples carrying the L452R mutation (carried mainly by the Delta variant) continued to decline, standing at 25.9% in S52 (vs. 57.1% in S51).

Sequencing data, which are the only way to identify variants, confirm a rapid increase in the spread of Omicron in mainland France: it accounted for 10.7% of interpretable sequences in the Flash S50 survey and 49% in the Flash S51 survey.

• Omicron Variant Focus - International Data and Investigations in France on page 8

Nearly 73% of those aged 65 and older have received their booster dose

On January 4, 2022, the estimated vaccination coverage in the general population based on Vaccin Covid was 77.2% for a complete primary vaccination series and 38.1% for the booster dose. Among those aged 12 and older, 89.8% had received a complete primary vaccination series. Among those aged 18 and older, 48.4% had received a booster dose, and 59.4% of those eligible for the booster as of that date had actually received it. Among those aged 65 and older, 72.9% had received a booster dose, and 82.4% of those eligible for the booster as of that date had received it. In addition, 2.5% of children aged 10 to 11 had received a first dose of the vaccine (0.6% for those aged 5 to 9). As of January 4, 2022, 93.0% of residents in nursing homes or long-term care facilities had received a full primary vaccination series, and 67.1% had received a booster dose. The percentage of these residents eligible for the booster shot who had actually received it was 73.5%. Furthermore, 58.6% of healthcare professionals working in nursing homes or long-term care facilities who were eligible for the booster shot had actually received it. This percentage was 78.6% for self-employed professionals and 59.8% for salaried professionals.

Discrepancies have been observed at the departmental level between the SIDEP data received by Santé publique France in recent days and the data available to the ARS. Epidemiological indicators (incidence rate, positivity rate, and testing rate) at the departmental level are therefore temporarily unavailable. Regional indicators are largely unaffected, with the exception of the Bourgogne-Franche-Comté and Martinique regions, and provide insight into the dynamics of the epidemic in the regions. National indicators are not affected. All stakeholders are working to resolve the issue as soon as possible.