Je n’ai aucune compétence pour parler du virus ou des vaccins. Je n’en parle donc pas.
J’ai été interessé par cet article de Yves Smith de Naked Capitalism, que je respecte . Je le porte à votre connaissance, il est plutot favorable au vaccin de Johnson & Johnson.
Posted on by Yves Smith
Yves here. We are running this post for one reason: as this article stresses, the testing of the Pfizer and Moderna vaccines was conducted much earlier, when fewer variants were out and about. Therefore the Johnson & Johnson vaccine efficacy gives a much more realistic of what you could expect in terms of protection now.
So far, with Pfizer and Moderna, all we have are airy assurances and largely in vitro studies against the new variants. Both companies have discussed the notion of a third “booster: shot to contend with known new variants, which looks an awful lot like an admission that they suspect or even know the efficacy of their current offerings is meaningfully lower against some of the new variants.
Another way the efficacy data may not be comparable is in how they screened for Covid infections. Astra Zeneca tested all its clinical trial participants every week. By contrast, Pfizer used the dodgy approach of testing ONLY participants who developed “severe respiratory symptoms”. That means they ignored cases with loss of smell, the most reliable indicator of Covid, ones with digestive symptoms. and other symptom combinations that the CDC (and people I know) have found to be signals of Covid onset: fever, chills, headache, fatigute. And the “severe respiratory infection” only screen also means Pfizer did not catch mild or asymptomatic cases, even though we know they can do serious damage. From CBS News:
A Texas trauma surgeon says it’s rare that X-rays from any of her COVID-19 patients come back without dense scarring. Dr. Brittany Bankhead-Kendall tweeted, “Post-COVID lungs look worse than any type of terrible smoker’s lung we’ve ever seen. And they collapse. And they clot off. And the shortness of breath lingers on… & on… & on.”
“Everyone’s just so worried about the mortality thing and that’s terrible and it’s awful,” she told CBS Dallas-Fort Worth. “But man, for all the survivors and the people who have tested positive this is — it’s going to be a problem.”
Bankhead-Kendall, an assistant professor of surgery with Texas Tech University, in Lubbock, has treated thousands of patients since the pandemic began in March.
She says patients who’ve had COVID-19 symptoms show a severe chest X-ray every time, and those who were asymptomatic show a severe chest X-ray 70% to 80% of the time.
In other words, I’m sufficiently suspicious of the Pfizer efficacy numbers as to be willing to give Johnson & Johnson a go, particularly with its one-shot drill.
By Maureen Ferran, Associate Professor of Biology, Rochester Institute of Technology. Originally published at The Conversation
The U.S. Food and Drug Administration has authorized the use of the Johnson & Johnson coronavirus vaccine in adults. Maureen Ferran, a virologist at the Rochester Institute of Technology, explains how this third authorized vaccine works and explores the differences between it and the Moderna and Pfizer–BioNTech vaccines that are already in use.
1. How Does the Johnson & Johnson Vaccine Work?
The Johnson & Johnson vaccine is what’s called a viral vector vaccine.
To create this vaccine, the Johnson & Johnson team took a harmless adenovirus – the viral vector – and replaced a small piece of its genetic instructions with coronavirus genes for the SARS-CoV-2 spike protein.
After this modified adenovirus is injected into someone’s arm, it enters the person’s cells. The cells then read the genetic instructions needed to make the spike protein and the vaccinated cells make and present the spike protein on their own surface. The person’s immune system then notices these foreign proteins and makes antibodies against them that will protect the person if they are ever exposed to SARS-CoV-2 in the future.Our daily newsletter
The adenovirus vector vaccine is safe because the adenovirus can’t replicate in human cells or cause disease, and the SARS-CoV-2 spike protein can’t cause COVID–19 without the rest of the coronavirus.
2. How Effective Is It?
The FDA’s analysis found that, in the U.S., the Johnson & Johnson COVID-19 vaccine was 72% effective at preventing all COVID-19 and 86% effective at preventing severe cases of the disease. While there is still a chance a vaccinated person could get sick, this suggests they would be much less likely to need hospitalization or to die from COVID-19.
A similar trial in South Africa, where a new, more contagious variant is dominant, produced similar results. Researchers found the Johnson & Johnson vaccine to be slightly less effective at preventing all illness there – 64% overall – but was still 82% effective at preventing severe disease. The FDA report also indicates that the vaccine protects against other variants from Britain and Brazil too.
3. How Is It Different from Other Vaccines?
The most basic difference is that the Johnson & Johnson vaccine is an adenovirus vector vaccine, while the Moderna and Pfizer vaccines are both mRNA vaccines. Messenger RNA vaccines use genetic instructions from the coronavirus to tell a person’s cells to make the spike protein, but these don’t use another virus as a vector. There are many practical differences, too.
Both of the mRNA-based vaccines require two shots. The Johnson & Johnson vaccine requires only a single dose. This is key when vaccines are in short supply.
The Johnson & Johnson vaccine can also be stored at much warmer temperatures than the mRNA vaccines. The mRNA vaccines must be shipped and stored at below–freezing or subzero temperatures and require a complicated cold chain to safely distribute them. The Johnson & Johnson vaccine can be stored for at least three months in a regular refrigerator, making it much easier to use and distribute.
As for efficacy, it is difficult to directly compare the Johnson & Johnson vaccine with the mRNA vaccines due to differences in how the clinical trials were designed. While the Moderna and Pfizer vaccines are reported to be approximately 95% effective at preventing illness from COVID–19, the trials were done over the summer and fall of 2020, before newer more contagious variants were circulating widely. The Moderna and Pfizer vaccines might not be as effective against the new variants, and Johnson & Johnson trials were done more recently and take into account the vaccine’s efficacy against these new variants.
4. Should I Choose One Vaccine Over Another?
Although the overall efficacy of the Moderna and Pfizer vaccines is higher than the Johnson & Johnson vaccine, you should not wait until you have your choice of vaccine – which is likely a long way off anyway. The Johnson & Johnson vaccine is nearly as good as the mRNA-based vaccines at preventing serious disease, and that’s what really matters.
The Johnson & Johnson vaccine and other viral-vector vaccines like the one from AstraZeneca are particularly important for the global vaccination effort. From a public health perspective, it’s important to have multiple COVID-19 vaccines, and the Johnson & Johnson vaccine is a very welcome addition to the vaccine arsenal. It doesn’t require a freezer, making it much easier to ship and store. It’s a one-shot vaccine, making logistics much easier compared with organizing two doses per person.
As many people as possible need to be vaccinated as quickly as possible to limit the development of new coronavirus variants. Johnson & Johnson is expected to ship out nearly four million doses as soon as the FDA grants emergency use authorization. Having a third authorized vaccine in the U.S. will be a big step towards meeting vaccination demand and stopping this pandemic.