Are we more contagious with the delta variant even if we are vaccinated

Thanks to SARS-CoV-2, we learned that "change is the only constant," as Heraclitus said. People have adapted to various changes this year and a half during the pandemic .

These changes include the spread of different variants, which depends in part, but not exclusively, on their genetic differences. These differences happen by chance. That is, an error in the replication of the genetic material of the virus causes a mutation .

The accumulation of a number of mutations gives rise to a variant, called a strain, when these changes affect the performance of the virus .

The Delta variant, the most transmissible at present

As far as we are concerned in this article, the delta variant (B.1.617.2) has been with us (at least) since December 2020. It has already become dominant in many countries in recent months. In fact, it represents additional than 96.5% of the latest cases identified in Spain .

The rapid and wide spread of this strain suggests that it is more transmissible than the alpha variant (line B.1.1.7). Its success appears to be due to the very fast replication and the generation of a viral load 1000 times higher. This would considerably reduce the incubation time required for transmission .

Does this lead to a higher severity of the disease?

However, there is still insufficient evidence to advise that this strain is more pathogenic. Let us recall, on the one hand, that this variant has led to an upsurge in the probability of hospitalization in the United Kingdom.

But, on the other hand, the available information from Public Health England (PHE) suggested that the case fatality rate (CFR) of this variant was lower than that of the alpha variant.

However, these comparisons between variants are complex and probably insufficient. Regardless of their genetics, the variants spread at very different times during the pandemic.

In addition, several issues come into play, such as the saturation of the health system, the state of vaccination and the age of infected people, which makes their management difficult.

How the vaccine responds to the delta variant

Today, more than 70% of the Spanish population has a comprehensive vaccination program. It is therefore worth asking whether these vaccines continue to protect us against the delta variant or whether, as has been speculated, we are more contagious despite vaccination.

To resolve this debate, we must first distinguish between protecting ourselves from infection and protecting ourselves from serious illness.

We knew that when the delta was not the dominant option, the vaccines authorized so far have been very effective in preventing grave illness, hospitalization and death.

But here, a study concludes that the effectiveness of the AstraZeneca vaccine against serious delta-caused diseases is 67% (74.5% against alpha), while that of Pfizer is in the order of 88% (94% against alpha).