The “superpower” of Pfizer and Moderna mRNA vaccines: could they slow the transmission of COVID-19?

To prevent COVID-19 and the serious consequences it could have on the body, any vaccine is good and recommended. Some formulas, such as those of Johnson & Johnson, Sputnik V and AstraZeneca, are based on adenovirus; others use the inactivated virus, such as Sinopharm’s. Corn For public health experts trying to stop a global pandemic, eliminating even the slightest infection is also crucial. Yes This is precisely where messenger RNA (mRNA) vaccines from Pfizer-BioNTech and Moderna come in.

“Not all COVID-19 vaccines are the same,” he says Eric Topol, doctor and scientist from the Scripps Research Translational Institute, in dialogue with the journal Science. “It is clear that both mRNA vaccines are very effective in preventing infections, and that one would not expect others to break the chain as well.”

Adele Butt, epidemiologist and infectious disease specialist with the Pittsburgh Veterans Affairs Health System, who also works at Weill Cornell Medicine, Qatar, also told the scientific journal: “It is very, very important to stop the transmission of the infection ”.

Last week at Annals of Internal Medicine, Butt and other researchers have published evidence showing that mRNA vaccines would be ideal to achieve this goal.

Scientists compared more than 54,000 veterans who tested for COVID-19 and tested positive with an equal number of people who tested negative, comparing each positive and negative case by age, sex and comorbidities. Using the immunization status of each participant, they calculated that the Pfizer and Moderna vaccines were, respectively, 96% and 98% effective in preventing SARS-CoV-2 infection.

Another study conducted in Qatar and published in the journal Natural medicine, used a similar approach to show that two doses of Moderna were 92.5% effective in preventing asymptomatic infections with any variant circulating at that time. They were also 100% effective against any Alpha variant infection and 96.4% against Beta variant infection.

A survey, this time in the United States, used a different conception. Almost 4,000 frontline workers have been tested every week, whether or not they show symptoms. Complete vaccination with Pfizer or Moderna vaccines were 90% effective against any infection, the researchers reported in the Weekly Morbidity and Mortality Report of the CDC.

However, these studies were performed before the spread of the Delta variant, for which actual data on asymptomatic infections are still lacking. But so far, the results are promising and would indicate that mRNA vaccines can also inhibit asymptomatic Delta infection.

Topol notes that a large real-world study from the UK, published last week in The New England Journal of Medicine, found that Pfizer vaccine outperformed AstraZeneca vaccine in preventing symptomatic Delta variant infection by 21 points, by 88% to 67%.

This substantial margin “This will likely result in better suppression of transmission, unlike the similarities of vaccines in reducing hospitalizations and deaths.”, from Topol.

Many scientists suspect that mRNA vaccines outperform others in preventing infections because of high levels of antibodies that block viruses, called neutralizing antibodies (NAB), which generate. “The mRNA vaccines build the immune system in a way that appears to be better and to a greater extent than some of the other approaches,” although no one knows why, he said. Science Larry Corey, vaccinologist at the Fred Hutchinson Cancer Research Center.

Some say that the performance of mRNA vaccines suggests that they should be widely distributed in the poorest countries, which until now have relied mainly on AstraZeneca and Russian and Chinese vaccines. “There is something special here,” with mRNA vaccines, says Corey. “Let’s embrace this and think about making it public policy.” Yes indeed, the scientist urges lawmakers to bring these “more potent vaccines … to low- and middle-income countries”.

How do they work

All vaccines have the same goal: train the immune system to recognize the coronavirus and thus raise its defenses in a preventive manner, in order to neutralize the real virus in the event of contagion.

With that of Pfizer and its German partner BioNTech, as well as that of the American company Moderna, strands of genetic instructions called messenger RNA are injected into the body, that is, the molecule that tells our cells what to do. Each cell is a mini-factory of proteins, according to the genetic instructions contained in the DNA of its nucleus.

The vaccine’s messenger RNA It is made in the laboratory. Thanks to the vaccine, it is inserted into the body and take control of this machinery to manufacture specific proteins or antigens of the coronavirus: its “spicules”, these very characteristic points which are on its surface and allow it to adhere to human cells in order to penetrate them.

These proteins, harmless in themselves, They will be released by our cells after receiving instructions for the vaccine, and the immune system will produce antibodies in response. These antibodies will remain on guard for a long time – as expected – with the power to recognize and neutralize the coronavirus in case it infects us.

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