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By Sangmi Cha
SEOUL, July 26 (Reuters) - A mixed vaccination of first
AstraZeneca and then a Pfizer COVID-19 shot
boosted neutralizing 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.
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 Pfizer shots.
A British study last month showed similar results - an
AstraZeneca shot followed by Pfizer produced the best T-cell
responses, and a higher antibody response than Pfizer followed
by AstraZeneca.
The data provides further support for the decision of
several countries to offer alternatives to AstraZeneca as a
second shot after the vaccine was linked to rare blood clots.
The South Korean study also analysed neutralizing activity
against major variants of concern, the Korea Disease Control and
Prevention Agency (KDCA) said.
None of the groups demonstrated reduced neutralising
activity against the Alpha variant, first identified in Britain,
but the neutralization titre decreased by 2.5 to 6 fold against
Beta, Gamma and Delta, first detected in South Africa, Brazil
and India respectively.
(Reporting by Sangmi Cha; Editing by Miyoung Kim and Nick
Macfie)
