(Reuters) – Data from a small, early-stage safety trial testing Moderna Inc’s <MRNA.O> experimental COVID-19 vaccine does not provide critical data to assess its effectiveness, Stat News reported on Tuesday, citing experts.

The health news publication’s report https://bit.ly/36kKerh pulled down shares of the Cambridge, Massachusetts-based biotech and erased modest gains on the benchmark S&P 500 index <.SPX>.

Moderna said on Monday the vaccine candidate, the first to be tested in the United States, produced protective antibodies in a small group of healthy volunteers.

The news based on data from eight people who took part in a 45-subject safety trial sent the company’s shares up nearly 20% on Monday and also pushed the markets higher.

Moderna did not immediately respond to a Reuters’ request for comment.

The company’s shares closed down 10.4% at $71.67.

(The story corrects shares close to $71.67, from 471.67, in last paragraph)

(Reporting by Manojna Maddipatla in Bengaluru; Editing by Sriraj Kalluvila)