This kind of data, already used in many foreign countries, had been eagerly awaited for several weeks in France.
A study by the DREES (Directorate of Research, Studies, Evaluation and Statistics), published this Thursday evening and that Le Parisien was able to consult in preview, provides initial information on the vaccination status of infected people by SARS-CoV-2 and in particular by its variant Delta in France.
Read also Delta variant: this is what the "fourth wave" could look like in the hospital
First element: only 6% of the cases tested positive for Covid-19 from June 28 to July 4 concern people fully vaccinated while at the same date, 32% of the inhabitants had completed their vaccination cycle.
11% of cases had received their first dose for more than 14 days or their second dose for less than 7 days, 3% had recently received their first injection, and 80% had received no vaccine dose.
Regardless of the age group, "the proportion of people fully vaccinated among positive cases remains significantly lower than complete vaccination coverage," says Drees.
In 70-80 year olds, for example, 30% of positive cases were fully vaccinated even though full vaccination coverage exceeded 70%.
Among 30-40 year olds, these rates are, respectively, about 5 and 20%.
Beware of interpretation
This finding corroborates the effectiveness of vaccination, even against simple infection.
If we only take into account symptomatic cases (all ages combined), the proportion of fully vaccinated even drops to 4% (9% received their first dose for more than 14 days or their second dose for less than 7 days, 4 % recently received their first injection, and 83% had not received any vaccine doses).
This corresponds to the rate of “96%” advanced by Olivier Véran this Thursday afternoon.
96% of # covid19 positive patients with symptoms were not vaccinated.
The vaccine protects you.
The vaccine protects us.
- Olivier Véran (@olivierveran) July 15, 2021
One point seems reassuring about the effectiveness of vaccines specifically against the Delta variant, now the majority in France. Taking into account only the screened positive tests bearing the L452R mutation (which corresponds to a suspicion of a Delta variant), we find 5.5% of completely vaccinated people among the positive cases and 4.7% among those symptomatic. The numbers are certainly small, but the rates are very close to those obtained against all strains of the virus. "The protective effect of vaccination against infection does not appear to be significantly different for this particular mutation," concludes Drees.
However, several biases, in particular the fact that the vaccinees are probably less tested, can exist.
This is why these “descriptive” data do not allow “a precise estimate of the vaccine efficacy”, indicates the Drees.
For that, it would also be necessary to work on data department by department, the vaccination coverage not being exactly the same on the whole of the territory.
No data yet for hospitalizations
As we explained at the end of June, and as the infographic below shows, care must be taken when interpreting this kind of data. In fact, the greater the vaccination coverage, the more the proportion of vaccinated among the positive cases will grow… without this jeopardizing the effectiveness of the vaccines. Taking the reasoning to the extreme, if 100% of the inhabitants were vaccinated, 100% of symptomatic cases would be vaccinated.
Such “cross-referenced” data for hospitalizations are not available.
Olivier Véran spoke Tuesday evening of the first figures - "100% of patients recently admitted to intensive care and 93% of those admitted to medicine in 30 large hospitals are not vaccinated" -, but the crossing of the SI-VIC databases (the hospitalizations) and VAC-SI (vaccination) is not yet operational at the national level.
Whether for Pfizer, Moderna or AstraZeneca, the known data show, however, that the efficacy is much stronger against severe forms than against simple symptoms of the disease.
According to Public Health England, two doses of Pfizer and two doses of AstraZenea reduce the risk of being hospitalized following an infection with the Delta variant by 96% and 92%, respectively.
