(Bloomberg) -- A group of international scientists questioned results from a study of Russia’s fast-moving coronavirus vaccine that were published in the Lancet medical journal, saying some of the findings appeared improbable.

The researchers flagged concerns over seemingly identical levels of antibodies in a number of study participants who were inoculated with the experimental vaccine. This and other patterns in the data present “several different points of concern,” according to an open letter written by Temple University professor Enrico Bucci and signed by more than a dozen other scientists.

The Lancet published results of the early-stage trial last week, offering the first look at the Russian study to be vetted by outside experts. A move by the government to approve the shot for use based on the initial results had drawn widespread skepticism, since vaccines aren’t normally cleared before broad assessments of their efficacy and safety.

The Lancet said it encourages debate on papers that it’s published.

“We have shared the letter directly with the authors and encouraged them to engage in the scientific discussion,” the journal said in a statement.

The Gamaleya Research Institute of Epidemiology and Microbiology, which is developing the vaccine, told the news portal Meduza that there were no errors in the study.

”If the Lancet’s editorial board asks for clarification, we are ready to answer,” Deputy Director Denis Logunov told Meduza, adding that he isn’t planning to answer the scientists behind the open letter.

A Gamaleya spokesman couldn’t be reached by phone for comment.

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