The study said that blood taken from people who had been given the vaccine neutralized an engineered version of the virus that contained the same mutations carried on the spike portion of the highly contagious P.1 variant first identified in Brazil.

The scientists said the neutralizing ability was roughly equivalent the vaccine’s effect on a previous less contagious version of the virus from last year.

The spike, used by the virus to enter human cells, is the primary target of many COVID-19 vaccines.