Key Points

• In Week 15 (April 12–18, 2021), epidemiological indicators of SARS-CoV-2 circulation in Île-de-France remained at a very high level. A downward trend in the indicators was observed, but pressure on hospitals remained high and persistent in the region.

• The incidence rate continued to decline in Week 15, but this decrease was partly due to the continued decline in the testing rate. The increase in the positivity rate, which was particularly marked in Week 14, continued but at a more moderate pace in Week 15. The incidence rate was lowest among those aged 75 and older, possibly due to the vaccination coverage achieved in this more vulnerable population; however, the rise in the positivity rate in this age group could reflect lower adherence to preventive measures amid active viral circulation.

• In Week 15, visits to primary care for “suspected COVID-19” stabilized, and visits to emergency care decreased slightly. However, the strain on the hospital system, which had been very high for several weeks in Île-de-France, persisted. The number of new hospitalizations showed a very slight downward trend for the first time in 8 weeks, but the number of hospitalized COVID-19 patients and the number of patients in critical care remained at very high levels. The number of COVID-19 deaths in hospitals stabilized at a high level, and Île-de-France was already, in Week 14, the region with the highest excess mortality from all causes.

• Variants of concern, known to be more transmissible and responsible for more severe cases, remained largely predominant in Week 15. The proportion of suspected cases of the 20I/591Y.V1 (UK) variant, which accounted for 69.8% of screened tests, was declining in Île-de-France, while the proportion of suspected cases of the 20H/501Y.V2 or 20J/501Y.V3 variants, at 6.6%, was increasing in Week 15.

• At the same time, COVID-19 vaccination continued to progress in Week 15 in Île-de-France. As of April 20, 2021, 1,931,161 residents of Île-de-France had received at least one dose of the vaccine, representing a vaccination coverage rate of 15.7% (vs. 14.1% in Week 14).

• Although the decline in certain epidemiological indicators might suggest the beginning of a slowdown in SARS-CoV-2 transmission, transmission rates remained high in Île-de-France. Furthermore, the decline in testing rates calls for caution in interpreting the dynamics of the epidemic. In this context, limiting contacts—particularly during family gatherings—consistently practicing preventive measures, and adhering to the recently strengthened public health measures are essential for everyone, including those who have been vaccinated.