Russia’s Sputnik V demonstrated more than two times higher virus neutralizing activity against the Omicron variant in comparison to the Pfizer coronavirus vaccine, according to a study of blood samples, released Thursday by the National Institute for Infectious Diseases Lazzaro Spallanzani in Italy and Russia’s Gamaleya Center.

The research was prepared by a team of 21 Russian and Italian scientists and published on the preprint health sciences website MedRxiv. It has not yet been peer-reviewed.

The study tested neutralizing antibodies performance against Omicron in 31 samples from people who had been twice vaccinated with Sputnik against 51 samples from people twice vaccinated with the Pfizer mRNA vaccine, over different points in time.

The study, if validated by a peer review, would contribute to some emerging claims that certain types of more “conventional” vaccines could in fact provide more durable protection over time  against a constantly mutating virus than the cutting edge mRNA versions – although this remains a point of emerging debate.