For three weeks, the number of Covid-19 cases has increased on a sliding average over seven days in England, from 2,000 in mid-May to nearly 6,000 in early June, and 8,000 daily cases on June 11. The Delta variant, known as “Indian”, is now the majority, representing nearly 74% of cases. The country is suspended from the upcoming decisions of the Prime Minister, who could postpone the last stage of deconfinement.
In Portugal also, the incidence has increased since the second week of May: around 400 cases were recorded there on May 8, and 900 on June 10. In the week of May 17-22, samples uploaded to the Gisaid database were almost 50% Delta variants (18 of 38). The United Kingdom has decided to take Portugal off its green list and now imposes a quarantine on travelers from this country.
Germany counts, for its part, 50% of additional Delta sequences in less than two weeks (517 cases on June 11) and Belgium 60% more (191 cases), when France has 130 cases, against 80 at 31 may. Nevertheless, the Alpha variant remains dominant in France: according to the French Public Health Flash survey dated May 25, it then represented 87.8% and the Delta variant 0.5% of the 800 sequences studied. On May 11, date of the last known complete results, the proportion of Delta was 0.2% in the 1,700 sequences analyzed.
The vaccine still effective
In England, the last technical update from Public Health England, on June 11, confirms the superiority of the Delta variant over Alpha in terms of distribution, without the exact value of its contagiousness can be firmly determined. Several experts evoke a contagiousness of about 60%, that is to say of the order of the superiority of the Alpha compared to the historical strain of the virus. This greater transmission may be explained by increased contagiousness or an ability to escape antibodies, or both, but no studies have yet been published to clarify the intensity of either path.
The British technical analysis also indicates that preliminary data in England and Scotland show a higher risk of hospitalization for the Delta variant than for the Alpha, responsible for the last epidemic wave.
Several studies have already shown that the efficacy of two doses of Pfizer-BioNTech vaccines remains good: according to the Pasteur Institute, it is 93.4% for the Alpha line and 87.9% for the Delta. In the review Nature of June 10, a research team associating universities and the company showed, in vitro, that the effectiveness also remains good with the vaccine prototype developed against the Beta variant, known as “South African”, known to be the one which decreases the vaccine effect the most.