Asked on Twitter on June 24
In the UK, 84.6% of the adult population has received at least one dose of vaccine and 62.1% is fully vaccinated. However, with more than 16,000 new contaminations on Monday (on average over seven days), the vast majority of them caused by the delta variant, the curve of infections linked to Covid-19 across the Channel has been increasing for several weeks. According to Nadhim Zahawi, the minister in charge of vaccination, however, it shows its effectiveness, since “Less than one in ten people hospitalized because of the delta variant received two doses of the vaccine.”
Where do these numbers come from? In a weekly report on variant surveillance, the British health agency Public Health England (PHE) has provided data on the share of vaccinated among confirmed cases of delta variant by sequencing or genotyping, only in England, since the beginning of February.
About 92,000 infections by this variant were identified between February 1 and June 21 (including nearly 80,000 in the last twenty-eight days), according to the last bulletin published Friday. In almost 66.4% of the delta variant cases for which the vaccination status is known (81,014 cases), the infected persons were not vaccinated; 7.7% had received a first dose for less than 21 days, 16.9% for more than 21 days, and 8.9% had two doses. Those under 50 are over-represented since they represent 89.6% of cases. The latter were (still for those whose vaccination status is known) 72.8% unvaccinated.
Only 3% with less than two doses
The PHE also provides information on the number of hospitalizations after an emergency room visit among people infected with the delta variant. In all, over the same period, 745 people were admitted overnight, 65.9% of whom were unvaccinated and only 10.8% with two doses. Here again, the under 50s are in the majority (75.7% of hospitalizations) and 77.7% unvaccinated. Only 3% had received two doses.
Please note, however, that these data do not specify the context of the admission. They also do not allow to have a complete vision of the number of cases of Covid-19 in the hospital. “Cases for which the date of the sample is the same as the date of the emergency room visit are excluded in order to rule out cases detected by routine testing in health care facilities where the main cause of presence is not is not the Covid-19. This underestimates the number of people hospitalized with Covid-19, but only includes those who tested positive before the day of their emergency room visit ”, specifies the PHE. When contacted, Public Health England explains: “Patient confidentiality would not allow us to comment on an individual’s situation.”
Finally, still since early February, 117 deaths “Within twenty-eight days of the date of the positive sample” to the delta variant were recorded by the PHE. In detail, 109 cases are over 50 years old, of which 68 are vaccinated (50 with two doses, 18 with one dose) and 38 were unvaccinated. In those under 50 (eight cases), two people had received a dose more than 21 days ago, and six were unvaccinated. In total, the case fatality rate for the cohort studied would therefore be 0.13%, much lower, for the moment, than the rate observed so far (around 1%). A provisional and incomplete rate, however. First, because deaths will still occur among this group of infected in the next four weeks. But also because the inventory of cases of contamination, which is used here as a denominator, is not exhaustive, people having been infected without knowing it. As a reminder, Public Health England estimated that Pfizer protected 96% and AstraZeneca 92% against serious forms related to the delta variant leading to hospitalizations.
Number of deaths to be taken with caution
Asked about the presence of vaccinated patients among the deceased, the PHE explains that in the event of high vaccination coverage, “Even with a very effective vaccine, it is expected that a large part of the cases will occur in vaccinated individuals, simply because a larger part of the population is vaccinated than not vaccinated.”
And this, all the more “If the vaccination has targeted as a priority the people most likely or most at risk of developing a severe form, as is the case in the United Kingdom […], people belonging to at-risk groups may also be at greater risk of hospitalization or death from causes other than Covid-19, and therefore may be hospitalized or die with Covid-19 rather than from the Covid-19 “, specifies the PHE.
It should also be noted that the number of deaths provided by the agency in this report should be taken with caution. Indeed, these are only people who died with Covid-19 within twenty-eight days after the positive test. This indicator therefore incorporates potential deaths caused by other causes while at the same time excluding deaths linked to Covid-19 occurring beyond twenty-eight days. In a post published on the official blog of the PHE in August 2020, epidemiologist John Newton, director of “Improving health” at the PHE, explained this choice which is based in particular on an analysis of the time between the date of the positive test and death. At the time, out of 41,598 deaths from Covid-19 cases reported as of August 3, 2020, 88% had occurred within 28 days. By giving the number of deaths that occurred in the twenty-eight days, “The objective is to provide a main indicator of the immediate impact of the epidemic”, he concludes.