Covid-19: constrained vaccine strategies and other scientific news
Coronavirus test center (illustrative image).
REUTERS - LUCY NICHOLSON
Text by: Simon Rozé Follow
5 mins
Vaccines against Covid-19 are still talking about them: after the announcements of the results of clinical trials, authorizations are now starting to be issued.
This was particularly the case in the United Kingdom, from this Wednesday, December 2, 2020.
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After this authorization, London intends to start the vaccination campaign next week.
It is the vaccine developed by Pfizer and BioNtech that is concerned, but it is however regrettable that the data of the phase 3 clinical trial, at the end of which the laboratory affirmed that its product is 95% effective, no have still not been published.
The health authorities have this data, thousands of pages, which allowed them to issue this authorization notice, but while the mistrust against vaccines is reaching record levels, it would be welcome if it was even accessible to the scientific community. and to the general public before the first doses are given.
Why prioritize the people to be vaccinated?
The British vaccination campaign will primarily and initially concern the most vulnerable people, as in France.
There are two main reasons for this.
First of all, stocks are tight and it is impossible to vaccinate everyone right now.
The second reason is due to the nature of the vaccine itself.
The available data show that while it is effective in preventing severe forms of Covid-19, it is not known whether it prevents infections.
These limits set, the health authorities are therefore focusing on the people to be protected as a priority.
However, this could evolve with more hindsight.
If it turns out that these vaccines also protect against infections, the timing of the different phases of vaccination would be changed.
To be sure, clinical trials are still ongoing or about to begin even as the marketing authorizations begin to be granted.
It is now a question of refining the data already available.
“
For transmission, we are going to study more specifically whether vaccines provide a mucosal response,”
explains Odile Launay, who
heads
the
Covireivac
platform
for French clinical trials.
“
There will also be population data
”
once the vaccination campaigns have started.
“
They give you an idea of the impact of vaccination on the population, whether or not they are vaccinated.
When we started vaccination against pneumococcus in children, we realized that there was a decrease in cases in the elderly who had not been vaccinated.
The vaccine had an impact on the risk of transmission from toddlers to seniors.
"
New clinical trials
The continuation of these clinical trials may also help answer specific questions.
Thus, the vaccine from Moderna will be tested again in France, during a phase 2 clinical trial, while its phase 3 has already delivered its findings with 94.5% effectiveness announced.
However, these are general population data.
What about the particular subgroup of people over 65?
This is the type of question that the French essay must answer.
180 people, including 120 over 70 years old will participate in France.
In parallel, two other trials, phase 3 this time, will concern vaccines developed by Astra Zeneca and Janssen.
New hope for cross immunity?
The Sars-CoV-2 responsible for Covid-19 is just one coronavirus among others in this family.
There are 6 others that target humans, including two responsible for deadly epidemics: Mers-CoV and Sars-CoV-1.
The last 4 are much milder and only cause colds.
The cross-immunity hypothesis suggests that if we have been infected with a "nice" coronavirus, our immune system would then have some weapons to fight its cousin Sars-CoV-2.
The first
in vitro
work
had raised hope;
quickly disappointed with clinical trials.
This hope is now renewed by a study published in the
Journal of Clinical Investigation
.
The authors formed two groups: one whose members were infected with a benign coronavirus, the other in which this is not the case.
They then compared the number of Covid-19 patients in the two groups.
The researchers then realized that they were equivalent.
On the other hand, in the group previously contaminated by "nice" coronaviruses, much less hospitalization and deaths caused by Covid-19.
Cross-immunity would therefore not protect against infection but to some extent prevent its severe forms.
This would also explain why children have few severe forms of Covid-19, since they are very sensitive to mild coronaviruses.
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