According to the Centers for Disease Prevention and Control (the main health agency in the United States), the Moderna vaccine is superior to Pfizer against severe forms of the disease, especially over time. After 120 days, Moderna protects 92% and Pfizer 77%.
CDC researchers analyzed a sample of nearly 3,700 adults hospitalized with Covid-19 associated with severe symptoms. The study was conducted between March 11 and August 15, 2021, a period that precedes and includes the predominance of the Delta variant, reports AFP.
Over time, the loss of effectiveness of the Pfizer vaccine is clearer:
- Pfizer’s effectiveness rate goes from 91% over the period of 14 to 120 days after the injection to 77% for the period after 120 days.
- In comparison, over the same periods, the effectiveness rate of Moderna’s vaccine rose from 93% to 92%.
The Moderna vaccine better blocks the transmission of the virus
According to a prepublication posted online last August by the famous Mayo Clinic (in the United States), RNA vaccines would be effective against the Delta variant – they would in particular prevent hospitalizations.
But according to this same study, the Moderna vaccine would be significantly more effective than the Pfizer / BioNtech vaccine. to limit the transmission of the Delta variant : 76% against “only” 42%.
How to explain this difference? According to Antoine Flahault, epidemiologist and director of the Institute of Global Health in Geneva, Switzerland, interviewed by our colleagues from Paris, it would be a question of dosage: “When a person is vaccinated with Pfizer’s formula, they receive 30 micrograms of messenger RNA in 0.3 ml of saline. For Moderna’s formula, it’s 100 micrograms in 0.5 ml of saline. This is the only major difference between the two vaccines.”
This Tuesday, August 17, the Ministry of Health recalled that this “pre-print” publication had not yet been validated and was therefore not the subject of a scientific consensus. However, he indicated that the Moderna vaccine could be more effective, due to less adaptation of the virus, because it is much less used in the vaccinated population.
In other words, the virus mainly encountering people vaccinated with Pfizer, it would try to circumvent it as a priority, in order to contaminate more people. Remember that in France, the Pfizer vaccine is overwhelmingly chosen. This underlines the interest of multiplying the types of vaccines.
Sources:
- Comparative Effectiveness of Moderna, Pfizer-BioNTech, and Janssen (Johnson & Johnson) Vaccines in preventing COVID-19 hospitalizations among adults without immunocompromising conditions, march–august 202, CDCSeptember 17, 2021.
- Comparison of two highly-effective mRNA vaccines for COVID-19 during periods of Alpha and Delta variant prevalenceAugust 9, 2021.
- Ministry of Health and Solidarity, August 17, 2021.
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