The Delta variant of Covid-19 is as contagious as chickenpox, probably has more serious effects than its predecessors and infected people seem to transmit it as much whether they are vaccinated or not, according to official US documents.
These findings, which are based on scientific studies, appear on a presentation circulating internally within the Centers for Disease Prevention and Control (CDC), the main health agency in the United States.
Revealed by the Washington Post, these documents, the authenticity of which has been confirmed to AFP, are accompanied by a warning to those responsible: “The war has changed”.
The director of the CDC relied on her conclusions to recommend again, for two days, the wearing of the mask indoors even for vaccinated people.
The presentation is based in particular on an analysis conducted in Provincetown, Massachusetts, where nearly 900 cases of Covid were detected after the July 4 National Day festivities, although three-quarters of the population has been vaccinated.
However, there was “no difference” in the viral load of vaccinated or unvaccinated people, according to the presentation of the CDC, which seems to indicate the same degree of contagiousness regardless of the vaccination status.
In contrast, there have been few hospitalizations (seven to date) and no deaths related to this outbreak, according to local news site Masslive.com.
What a finding “Is the main factor in changing the recommendations of the CDC” on the mask, Celine Gounder, an infectious disease specialist at New York University, told AFP: “This is not to protect vaccinated people who, if they are infected, will have mild symptoms, if any, but it is found that they can infect other people.”
In addition, CDC documents show that contaminations of vaccinated people are not as rare as previously thought with “35,000 symptomatic infections per week out of the 162 million Americans vaccinated.”
Based on international studies, the CDC judge that Covid was initially about as contagious as the flu, but has become comparable to chickenpox – one person infected with the delta variant transmitting it to eight others on average – still in below measles.
Data from Canada, Singapore and Scotland suggest it could be more dangerous, with more hospitalizations and deaths.
The effectiveness of vaccines vary, but in their presentation, the CDC estimates that the risk of dying or being seriously ill is divided by ten with a vaccine and the risk of being infected by at least three, which is to say that the vaccines are 90% effective against severe forms and 67% against infections.