What is known about Delta, the coronavirus variant that concerns scientists and authorities

Will he be an obstacle to deconfining in circles? The Delta variant of the new coronavirus is rife in the Landes, to the point that the Prime Minister, Jean Castex, traveling Thursday, June 24 in the department, warned that the lifting of the restrictions planned in France on 1is July could be postponed there if the epidemiological trend does not change. Delta does not strike only in the Sud-Ouest department, far from it. In the United Kingdom, he has already led Prime Minister Boris Johnson to postpone the “Liberation day” – namely the end of health restrictions -, scheduled for June 21. Who is Delta, and should we be concerned?

  • Indian or Delta, what’s the difference?

Delta is not exactly the new name of the variant that was first called “Indian” because it was first detected in India in October 2020. In fact, the known “Indian” variants are three, from the same line B.1.617, and Delta is the name given by the World Health Organization (WHO) to B.1.617.2. The institution had decided in early June to rename some of the more common variants. Let’s recap:

– Alpha is the so-called “British” variant, or B.1.1.7;

– Beta is the so-called “South African” variant, or B.1.351;

– Gamma is the so-called “Brazilian” variant, or P.1;

– Delta is one of the so-called “Indian” variants, or B.1.617.2;

– Kappa is his close cousin, also known as “Indian”, or B.1.617.1.

The variant is now present in at least 85 countries, according to the WHO, in varying proportions. In India, it quickly prevailed over its two cousins, while in the United Kingdom it took a few weeks for it to take precedence over the local variant. In the United States, it went from around 10% of positive samples sequenced on June 5, to 35% last week. A comparable proportion is observed in Israel. In the Democratic Republic of Congo and Uganda, it is responsible for around 77% and 97% of diagnosed cases, respectively.

In France, it represents more than 74% of positive tests carried out from June 14 to 20 in the Landes, according to the Regional Health Agency (ARS) Nouvelle-Aquitaine, against 12.1% in the Pyrénées-Orientales and Gironde, and 9.5% nationally. Government spokesman Gabriel Attal said on Wednesday that he was also responsible for several outbreaks in the Bas-Rhin.

  • Should we be worried?

Delta is a variant classified as “of concern” by the WHO (while Kappa, its close cousin, is only classified as “of interest”). This category includes variants likely to worsen the epidemiological situation, which turn out to be more virulent, or which modify the clinical picture of the infection with the new coronavirus, or which reduce the effect of public health measures, including vaccination. .

In a note communicated on June 23, the European Center for Disease Prevention and Control (ECDC) writes that Delta could be associated with a greater risk of hospitalization, i.e. severe form of Covid-19 . According to the ECDC, it has also been established that the first dose of vaccine, regardless of the product considered, offers less protection against Delta than against the other variants. On the other hand, once the two doses have been administered, the protection is almost equivalent.

In a detailed “preprint” study (that is to say not yet validated by peers) communicated on June 14, Public Health England, the British public health agency, advances converging results. According to her, two doses of Pfizer-BioNTech vaccine provide 88% protection against “Symptomatic forms” of Covid-19 due to the Delta variant, and 67% for the AstraZeneca vaccine. Against hospitalizations caused by Delta, the Pfizer vaccine is 96% effective after two doses, and that of AstraZeneca 92%.

Less encouraging, a study published by the journal Cell June 16 claims that Delta is stronger than some antibodies. Clearly, having already contracted Covid-19 would not always constitute a guarantee against reinfection by this variant. In detail, the antibodies produced during a first infection with the English variant would confer good protection against all the variants, but those developed following an infection with the Beta or Gamma variants would seem less effective in the event of re-infection with Delta.

Read the summary: New data on the Delta variant, on the rise in many countries
  • Can it cause a new epidemic wave?

Concerns focus mainly on the contagiousness of Delta. In its note of June 23, the ECDC specifies that, at this stage of knowledge, it turns out to be 40% to 60% more contagious than the so-called “British” variant, which played a major role in the third wave of the epidemic. in France. Delta should therefore represent 90% of new cases of Covid-19 in the European Union, by the end of August. “It is very likely that the Delta variant circulates widely during the summer, especially among young people who are not targeted for vaccination”, warned Andrea Ammon, director of the European Diseases Agency.

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A “preprint” study published on the site medRxiv on June 20, based on the analysis of more than 5,000 PCR tests, suggests that Delta is increasing rapidly in Ile-de-France and possibly in other regions of France. According to researcher Samuel Alizon and his colleagues at the CNRS at the University of Montpellier, he could thus “Cause a new epidemic wave from the month of August”.

  • Should we vaccinate, always vaccinate?

While increasing vaccination coverage therefore appears necessary to combat the Delta variant, this will undoubtedly not be sufficient. Indeed, the more contagious a virus, the higher the level of vaccination necessary to achieve group immunity (the threshold beyond which it can no longer circulate), explained Samuel Alizon to Agence France-Presse. .

However, with regard to the Delta variant, scientists agree that it would take more than 80% of the vaccinated population, especially since it partly escapes the immunity developed by people who have already contracted the vaccine. Covid-19. In these conditions, “Until most vulnerable people are protected, we must keep the circulation of the Delta virus low by strictly adhering to the public health measures that have worked to control the impact of other variants”, advocated Wednesday Andrea Ammon, of the ECDC.

After Delta, Delta +?

The Indian health authorities announced, Wednesday, June 23, to have recorded forty cases infected by a somewhat particular Delta variant: this one presents the K417N mutation, which Indian scientists, quoted by the Reuters agency, estimate that it could be synonymous with an even greater contagiousness. According to Reuters, the Indian health minister has warned that regions where the variant dubbed “Delta +” has been detected (Maharashtra, Kerala and Madhya Pradesh) “May have to strengthen their public health response by insisting on surveillance, the development of screening, rapid tracing of contacts.” Without forgetting, of course, the “Priority vaccination”.