A new medical study from South Korea says that a shot of the AstraZeneca coronavirus vaccine, followed by a shot of the Pfizer-BioNTech vaccine, can boost some antibody levels by six times compared to using just two shots of AstraZeneca instead.
The findings from Korea's Disease Control and Prevention agency follow a similar study in the UK last month.
The studies would support the decision by several countries to allow people who have had a single shot of AstraZeneca to use an alternative for their second dose after AstraZeneca was linked to rare bloodclots.
It includes Canada, Italy, and China -- although, the World Health Organization has warned against the practice, saying there isn't enough data about the health impact.
The South Korea study specifically focused on levels of what are called "neutralizing" antibodies, which prevent coronavirus from entering cells and replicating.