Seoul: Mixed vaccinations with AstraZeneca followed by Pfizer COVID-19 boosted neutralizing antibody levels sixfold compared to two doses of AstraZeneca, a study from South Korea found.
The study involved 499 healthcare workers – 100 received mixed doses, 200 received two doses of Pfizer / BioNTech vaccine, and the rest received two AstraZeneca injections.
All showed neutralizing antibodies that inhibit viral entry and replication, and the mixed vaccination schedule showed similar amounts of neutralizing antibodies found in the group that received two Pfizer injections.
A British study from last month showed similar results – the AstraZeneca injection, followed by Pfizer, caused a better T-cell response and a higher antibody response than Pfizer, followed by AstraZeneca.
These data further support the decision of several countries to offer alternatives to AstraZeneca as a second shot after the vaccine has been linked to rare blood clots.
The South Korean study also analyzed neutralizing activity against underlying causes of concern, the Korea Disease Control and Prevention Agency (KDCA) reported.
None of the groups showed reduced neutralizing activity against the Alpha variant first identified in the UK, but neutralization titer decreased 2.5-6 times against Beta, Gamma and Delta, first detected in South Africa, Brazil and India, respectively.