Covid-19: Delta variant drops vaccine effectiveness to 40%

The Delta variant, very contagious, reduced to 40% vaccine effectiveness against the transmission of the disease, the boss of theWHO, urging people to continue wearing masks and other barrier practices. ” The vaccines save lives, but they do not completely prevent the transmission of Covid-19 ”, Explained Tedros Adhanom Ghebreyesus during a regular press briefing devoted to the pandemic, which is wreaking havoc in Europe.

“ There is data which suggests that before the arrival of the Delta variant, vaccines reduced transmission by about 60%, with Delta this dropped to 40%, he stressed. In many countries and communities, we fear that there is this misconception that vaccines have ended the pandemic, and that people who are vaccinated no longer need to take other precautions. “.

700,000 dead by spring

The director general of the organization opened his traditional opening remarks on the situation in Europe, hit hard by a fifth wave infections, caused by a mixture of vaccination insufficient and loosening – probably premature in view of the dominance of the Delta variant in the region – in barrier gestures and restrictions.

” Over 60% of Covid infections and deaths worldwide last week were in Europe “, Recalled Doctor Tedros, adding that” this huge number of cases translates into an unbearable burden on health systems and exhausted health workers “. With more than 2.5 million cases and nearly 30,000 deaths recorded in the past week, the Old Continent is by far the region of the world most affected by the pandemic, according to official data collected by AFP. And the trend remains on the rise.

On Tuesday, WHO Europe was alarmed by the “grip” of the Covid-19 in Europe which could cause 700,000 additional deaths on the continent by the spring, in addition to the 1.5 million deaths already counted.

Even vaccinated, the risk of catching and transmitting the Delta variant is high!

Covid-19 vaccines protect against severe forms of this disease, but are not as effective at preventing infections and transmission since the Delta variant is in the majority. An English study looked at contaminations and the dynamics of contaminations within the home, where the coronavirus is most easily transmitted.

Article by Julie kern, published on November 3, 2021

It is at home, where barrier gestures and masks fall, that SARS-CoV-2 spreads most easily. The vaccination is an effective bulwark to reduce the risk of being contaminated, but far from being infallible, especially against the Delta variant. An English study, conducted atImperial College of London, concludes that a complete vaccination schedule confers very partial protection – but still greater than in the absence of vaccination – against the Delta variant in the context of domestic transmission.

” Our results show that vaccination alone is not sufficient to prevent people from becoming infected with the Delta variant, and spreading it beyond, into homes. This is probably the case for other enclosed places where people spend long periods of time nearby. This will happen more and more as we head into winter “, explains Ajit Lalvani, professor at National Heart & Lung Institute to theImperial College of London and who co-directed this study.

Transmission still possible despite vaccination

Between September 2020 and September 2021, scientists followed 621 participants identified by the contact tracing set up in the UK. The participants in this study, generally young and in good health, reported only mild or asymptomatic forms of Covid-19. Among them, 163 were tested positive for SARS-CoV-2: 71 by the Delta variant, 42 by the Alpha variant and 50 by the original variant. Among the 71 people infected with the Delta variant, 23 are unvaccinated, 10 partially vaccinated and 54 fully vaccinated. These 71 people are index case, that is to say that they are considered as the starting point of a chain of contamination. Scientists have regularly monitored and tested the people with whom the index cases have been in contact in their homes; these are the contact cases. In total, the 71 index cases attended 205 contact cases, of which 53 caught the coronavirus.

Among the 205 contact cases, 126 have a complete vaccination schedule, 39 are partially vaccinated and 40 are unvaccinated. The scientists then crossed the vaccination status of the contact cases tested positive for the Delta variant: 25% of them were fully vaccinated and 38% unvaccinated. While vaccination decreases the risk of being infected with the Delta variant, the probability of being infected remains significant. Using this data, scientists fromImperial College of London estimated the vaccines to be 34% effective in preventing infection with the Delta variant.

The peak of the viral cycle

In addition to monitoring contamination within homes, scientists also monitored the viral load in 133 patients, vaccinated or not. Every day, the amount of coronavirus in their body was estimated by PCR. Scientists have observed that the viral peak, the time when the number of virions is highest, is of the same magnitude in the vaccinated and the unvaccinated. British scientists believe that it is because of this very intense peak that the Delta variant manages to be transmitted so easily, even in vaccinated people. In contrast, the viral load decreases faster in people who have been vaccinated.

The work of scientists fromImperial College of London underlines an important fact: vaccination alone, especially against the Delta variant and at the onset of season cold is not sufficient to stem the transmission of SARS-CoV-2. Airing confined spaces, social distancing, masks or hand washing are all reflexes that break the chains of transmission. In addition, vaccines remain terribly effective in fulfilling their primary function: prevent severe forms and hospitalizations.