A study from South Korea revealed that a mixed vaccination of first AstraZeneca and then a Pfizer coronavirus shot boosted neutralizing antibody levels by six times compared with two AstraZeneca doses.

The study involved 499 medical workers, 100 of which received mixed doses, 200 taking two doses of the Pfizer-BioNTech shot and the remainder receiving two AstraZeneca shots.

All showed neutralizing antibodies, which prevent the virus from entering cells and replicating, and the result of the mixed schedule of vaccines showed similar amounts of neutralizing antibodies found from the group that received two shots of the Pfizer vaccine.

Notably, a British study last month showed similar results.

These data support the decision of several countries to offer alternatives to the AstraZeneca vaccine as a second shot, after linking this vaccine to the occurrence of blood clots.