UK: how the vaccine currently contains the Delta variant

At first glance, the numbers would be cause for concern.

The number of new daily cases of Covid-19 in the United Kingdom, where the Delta variant - more transmissible - is now in the majority, increased by 61% in one week.

This Wednesday evening, the curve should also "cross" that of France, in free fall for a month and a half.

And yet, if scientists and British authorities are generally concerned, one element has something to reassure them: the apparent effectiveness of vaccines. More than one in two British adults received two doses, twice as many as in France. In the most affected regions, such as the north-west of England, the increased incidence is hardly visible except among those under 60, and especially among young adults. However, the further down we go in the age groups, the fewer vaccines we find. Hospitalizations are also increasing, but in smaller proportions than new cases. And again, it is almost only among those under 65.

This is despite vaccines that offer good protection against hospitalization, so what's going on?

As ever, age breakdowns tell the story.

Hospital admissions remain low and flat among mostly-double-dosed older groups, but the increase is coming among younger adults.

pic.twitter.com/ZPNotB2k3R

- John Burn-Murdoch (@jburnmurdoch) June 8, 2021

Three reasons could explain why the growth of hospital admissions is slower than that of new cases.

First of all, there is always a lag of about ten days between the two curves, so you have to be careful in interpreting the data.

In addition, as we have seen, infected people are younger.

They are therefore less likely to be affected by a severe form of the disease.

Read also No deaths in 24 hours ... but exploding cases: why the Indian variant makes the British tremble

Finally, "people who have been vaccinated have little or no transmission of the virus and, in the event of infection, they have most often developed mild forms of the disease," said François Maignen, pharmacovigilance specialist based in London. .

“The vaccine breaks the links between infections, hospitalizations and deaths,” British Health Minister Matt Hancocq said in Parliament on Monday.

Race against time

According to data from Public Health England, the vast majority of confirmed cases of this Delta variant (so-called "Indian") and hospitalized patients had not been vaccinated, or had only received a first dose there. more than three weeks old.

Only 4% of positive people had had both injections, even though this is the case for 43% of the population of all ages.

One shining light however is that vaccination still appears to be making an impact on spread

73% of Delta cases are in unvaccinated people

Only 3.7% Delta cases are in people who've had both doses pic.twitter.com/zg6Yji76tr

- Meaghan Kall (@kallmemeg) June 3, 2021

In mid-May, the British health agency reported that Pfizer would prevent up to 87.9% of symptomatic forms due to the Delta variant at least two weeks after the second dose, against 93.4% against the Alpha variant ( "British"). Either a slightly reduced efficiency, but which remains good. The impact would be much greater after a single dose, since the effectiveness would be reduced by 20 points. And AstraZeneca, which is widely used in the United Kingdom, is showing less good results. But beware: these are only “observational” data, which may include certain biases. And we do not yet have scientific studies on the risk of transmission and that of severe form of the disease.

It is difficult to say who, in the short term, will win this “race against time” between variants and vaccination. A large part of the British population (almost 40%) has not yet received any dose and is therefore still particularly vulnerable. To maximize the chances on its side, the government lowered the age limit for getting vaccinated in England to 25 on Tuesday, against 30 years earlier. He could also decide to postpone for a few days or a few weeks the last stage of deconfinement, scheduled for June 21.