A mixed vaccination of first AstraZeneca and then a Pfizer Covid-19 shot boosted neutralising antibody levels by six times compared with two AstraZeneca doses, a study from South Korea showed.

The study involved 499 medical workers — 100 receiving mixed doses, 200 taking two doses of the Pfizer/BioNTech shot and the remainder getting two AstraZeneca shots, Reuters reports.

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