According to a study published in The New York Times, the Jansen vaccine is less effective against the delta variant.

The vaccine is also administered in Belgium and requires only one dose, producing fewer antibodies against the Delta variant. New York University researchers have found that the virus produces five times less antibodies that protect against this mutation.

“We do not want to discourage people from benefiting from the Johnson vaccine, but we hope that in the future it will be possible to get a second injection by Johnson or by Pfizer or Moderna,” said New York Times virologist Nathaniel, who led the study from Landau University.

Pfizer and Moderna vaccines, which require two doses, also produced fewer antibodies against the Delta variant, according to the study, although the difference is smaller than that of the Jansen vaccine.

U.S. health officials reported Tuesday that 83% of new coronavirus cases in the US are caused by the delta variant. At the beginning of the month, this ratio was still only 50%.

In Belgium, the delta variant represents 66% of coronavirus contamination in mid-July.