They were racing ahead of vaccination thanks to their in-house weapon – the Swedish-British vaccine designed by the University of Oxford and the AstraZeneca group -, saw the infection figures drop just a month ago and the prospect of ‘a total deconfinement approaching. But the tide has radically turned across the Channel. Boris Johnson announced, Monday, June 14, the postponement to July 19 of the last stage of lifting of the restrictions. Scheduled for June 21, it provided for, among other things, the reopening of nightclubs, authorization for theaters to return to full capacity, the end of gauges for gatherings and weddings, etc.
The rapid progression of the Delta variant – the new name of the “Indian” variant, according to the nomenclature adopted by the World Health Organization -, has come to play spoilers by sweeping its cousin Alpha, said to be “British”, responsible for the last epidemic wave that has grieved the country. Scientists’ concern grew and Mr Johnson had warned he wanted to take an approach “Irreversible” in terms of deconfinement.
A new deadline that is sure to anger part of Mr Johnson’s conservative camp, and which is a setback for the many companies that were hoping for a full summer reopening to make up for the losses of the past year. How to explain this turnaround?
1. What is the progression of the Delta variant?
After a long winter confinement and a vigorous vaccination campaign, the British government had gradually lifted various restrictions. But, after a drop in May, the contamination figures have recently started to rise again.
According to several British experts, the Delta variant is more contagious than the Alpha variant by around 60%, but is mainly responsible for the rise in infections: they tripled in three weeks, reaching nearly 8,000 cases on Friday, in the country on Friday. worst hit in Europe by the pandemic, with nearly 128,000 deaths. And the Delta variant is now the majority, representing nearly 74% of cases.
“Between half and three quarters of new positive cases are due to the variant B.1.617.2 [indien] », underlined the Minister of Health, Matt Hancock at the end of May. “This variant is becoming dominant [dans le pays], confirmed Jenny Harries, the head of the British health agency. It continues to progress, but we don’t know if it’s because it’s spreading or if it’s because we are testing more in the areas where it is circulating. “
In England, the last technical point of the health authorities, Public Health England (PHE), on June 11, confirmed the superiority of the Delta variant over the Alpha in terms of distribution, without the exact value of its contagiousness can be firmly determined.
This greater transmission may be explained by increased contagiousness or an ability to escape antibodies, or both, but no studies have yet been published to clarify the intensity of either path. PHE data also shows that preliminary data in England and Scotland show a higher risk of hospitalization for the Delta variant than for the Alpha.
2. How is the Delta variant distributed in the country?
The Delta variant is now present throughout the country, including London, but the epicenter of the infections is in the north-west of England and to a lesser extent in the Midlands.
Densely populated areas (Bolton, Blackburn or Leicester), where a significant part of the population lives in multigenerational households, and occupies service jobs in which teleworking is impossible. There are many inhabitants from the Indian subcontinent: the first people infected with the B.1.617.2 variant returned directly from India. In these areas, the British government sent the army to help with the accelerated vaccination of the populations.
3. How effective are vaccines against this variant?
According to a PHE study conducted between April 5 and May 16, the Pfizer-BioNTech vaccine was 88% effective against the Delta variant two weeks after the second dose (compared to 93% effectiveness against the Alpha variant), so that over the same period, the AstraZeneca vaccine is 60% effective against the Indian variant (against 66% against the English variant).
The two vaccines studied are 33% effective against the symptomatic disease caused by the Delta variant three weeks after the injection of the first dose, against about 50% against the Alpha variant, according to PHE. The coronavirus genome was sequenced for 12,675 cases included in this study, of which 1,054 were Indian variant cases.
4. AstraZeneca vaccines and long dose spacing
By postponing the last stage of its deconfinement, the British government intends to save time by vaccinating more people and thus protecting a larger part of the population against the virus.
But the epidemic resurgence in the country, which has, paradoxically, one of the most vaccinated populations in the world, thus raises the question of the effectiveness of AstraZeneca’s vaccine, which continues to be used mainly there: it represents the two thirds of inoculations. In March, the Prime Minister once again boasted, in a forum of the Times, a vaccine “Extremely” effective, after controversies related to fatal cases of thrombosis.
In addition to its high transmissibility, the Delta variant shows a great ability to infect people who have received only a single dose of vaccine, according to the PHE study. However, the country has not only opted to massively use a vaccine whose rate of protection against the Indian variant is found to be lower than those with messenger RNA, but also to delay the time between the first and the second dose, in order to increase the number. people who have received at least one dose. So if 79% of the UK adult population received a first dose, the figure drops to 56.6% for the second.
The latest PHE data had thus led the government to review its vaccination strategy and to accelerate the pace of second doses: on May 14, the British committee on vaccination had recommended reducing the time before the second injection to eight weeks, which was then twelve weeks.