A new American study, relayed by the newspaper “Le Monde”, suggests that the Pfizer vaccine would be less effective than Moderna against the risks of infection with the Delta variant. The results of the pre-publication study still need to be confirmed.

An American study, carried out by researchers at the Mayo Clinic and the data analysis company Nference, indicates that the Pfizer and Moderna vaccines would offer a high level of protection against the risks of severe forms but would have a difference in effectiveness against the risks of contamination. To reach this conclusion, the pre-publication study was based on hospitalization data and RT-PCR test results obtained between January and July, on more than 75 vaccinated or unvaccinated patients.

According to the results, pre-published on August 9 on MedRxiv, the two messenger RNA vaccines offer a significant and almost similar level of protection against severe forms of Covid-19 (75% for Pfizer and 76% for Moderna). On the other hand, the difference in effectiveness between the two vaccines widens when it comes to the risk of infection with the Delta variant (initially appeared in India). Indeed, the Moderna vaccine would be 76% effective against infection (symptomatic or not) against 42% for the Pfizer / BioNtech vaccine.

While this is the first comparative and quantified estimate, in real life, of the efficiency of the two messenger RNA vaccines, the results of the study remain to be confirmed for it to be the subject of a scientific publication. Indeed, the report has not yet undergone careful peer review and factors must be taken into account when reading the results.

According to Venky Soundararajan, lead author of the study, “ Based on the data we have so far, this is a combination of the two factors; The Moderna vaccine is probably – quite possibly – more effective than the Pfizer vaccine in areas where Delta is the dominant strain, and the Pfizer vaccine appears to have lower efficacy durability. “. In addition, it has been shown in previous studies that it takes about four times more antibodies to neutralize the Delta variant than it takes to neutralize the Alpha variant. Finally, it should be noted that the study does not take into account the serological status of the patients.