How well founded is the concern about the delta variant of Sars-Cov-2?

Scientific and epidemiological data suggest that the delta variant, formerly known as B.1.617.2 or "Indian", is currently the one to keep an eye on. There are still several elements of uncertainty, but full vaccination coverage still seems to provide good protection

(illustration: Getty Images) If there is one thing that the approximately 15 months of pandemic we have experienced have consistently confirmed, it is the difficulty to make medium and long-term forecasts on how the epidemiological situation will evolve, both in Italy and in the rest of the world. With the complication, especially in recent months, of the presence of different variants of the Sars-Cov-2 coronavirus, with non-homogeneous characteristics in terms of contagiousness, lethality and reactivity with the vaccine formulations approved and in use.

At the moment the viral variant that has gained the most media attention is the one now called delta, known in purely scientific terms as B.1.617.2 and containing E484Q and L452R as main mutations, for the first time combined together. At a colloquial and media level there are those who continue to call the Indian variant (because in India it initially spread significantly), even if in reality both the delta and the kappa variant pass under that name, which were initially told as a thing alone.

In recent days, more than for India, there has been talk of a delta variant for Europe and in particular for the United Kingdom, given that epidemiological statistics indicate that it is the protagonist of the modest (but a significant percentage) surge in recorded cases of infection that has occurred recently. Raising some concern not only across the Channel, but also throughout the European Union. But does it really make sense to fear this variant? Let's go in order.

The delta variant and the United Kingdom, in figures

More than the abstract evaluations, it is above all the numerical data to give an idea of ​​the epidemiological situation. Over the last week, the cases recorded in the country have risen from an average of about 3 thousand per day to peaks of around 6 thousand, therefore with a substantial doubling in a very short time. The absolute majority of these new cases, in some locations up to 75%, correspond to a delta variant infection, which therefore seems to have already become the dominant variant even with respect to the alpha variant (the one we called English).



According to the statistics elaborated by Public Health England (Phe), the delta variant would have a capacity to be transmitted from person to person about 50% higher than the alpha, and overall - at the same rate as the others conditions and risk factors - determines a 2.5 times higher probability of developing serious illness and requiring hospitalization. There is also talk of a typical symptomatology that includes gastric disturbances, hearing disorders and a higher risk of thrombosis, but a solid basis of scientific studies is still lacking on these elements.

If these data could cause some alarmism , and the trend of rapid growth only accentuates this more than reasonable concern, however it must be said that the absolute numbers at the moment are still quite low. Overall, in the United Kingdom we have (according to the latest available statistics of this type) 12,383 confirmed cases of contagion from the delta variant, and the daily bulletin speaks of a dozen deaths a day and a thousand people currently hospitalized. Numbers, as already mentioned, far worse than last week (in which there were also zero deaths), but still minimal compared to the peaks of the pandemic waves of the cold season just passed, where there were also 60 thousand new infections and 1,500 deaths in a only day. What is worrying is therefore above all the prospect, while for now in terms of emergency management the situation remains under control.

Delta variant against vaccines

Naturally the question of the questions - to which we immediately anticipate that there is no definitive answer - it is to what extent the delta variant is capable of escaping the protective action of vaccines. As we have already told here on Wired, the information in general is still preliminary (also because there are many vaccines to consider), and only for the formulation of Pfizer and BioNTech we have quantitative scientific studies of a certain reliability. For AstraZeneca's Vaxzevria there is a rough estimate of 60% efficacy, and for the other vaccines we are barely at the qualitative and anecdotal evaluations.

Two kinds of data are significant to tell in this regard. The first, on the front of the bad news, is that the delta variant seems to reduce the number of protective antibodies generated, by 2-6 times compared to the other variants and by 5-8 times compared to the initial form of Sars-Cov-2. Although it is not clear what the correlation between lower antibody response and loss of vaccine efficacy is, it is still a potentially critical element. On the good news front, however, there is that overall the complete vaccination cycle seems to continue to give good guarantees, at least in terms of protection from the more serious forms of Covid-19. According to a study conducted by the US Centers for Disease Control and Prevention (Cdc), there is talk of a protection even close to 90% for messenger rna vaccines, but these are still evolving estimates.

Numbers at the hand, in the United Kingdom of the more than 12,000 confirmed cases of contagion, 126 patients needed hospitalization, and 86 of these were not vaccinated even with a dose. According to press sources, only in 3 cases the hospitalization involved people who had already completed the cycle with the two scheduled administrations. This means, even without wanting to draw definitive quantitative conclusions, that in general vaccines maintain a certain protective efficacy even against the delta variant, even if they are unable to completely avoid severe cases of the disease.

High attention for all

According to the latest available data, the diffusion of the delta variant in the United States is estimated to be close to 6%, although it is considered plausible that the real figure is a little higher. And if the highest contagiousness is really confirmed compared to the other variants, it is more than plausible that even overseas it will soon become the dominant one in terms of circulation. At the moment, at least according to the information we have, the delta seems to have spread mainly among young people.

Although the conclusion of the first vaccination campaign is unlikely to coincide with the end of the pandemic, what many experts say all over the world are arguing (most recently Anthony Fauci in the United States) is on the one hand the need to speed up vaccine administration as much as possible, making the most of the level of protection guaranteed by approved formulations. Even with less than 100% efficacy in preventing severe forms, in any case the effect of vaccination coverage is felt at the general population level. On the other hand, the importance of continuing to keep the containment and protection measures active - from the mask to hygiene and distancing - is emphasized, even more so against a variant that seems to have a greater capacity to spread than the others.


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