Combination of AstraZeneca and Pfizer doses increases coronavirus antibody levels – study

RIO DE JANEIRO, BRAZIL – The combination of AstraZeneca’s first dose of Covid-19 vaccine and Pfizer’s second dose increased neutralizing antibody levels six-fold compared with two doses of AstraZeneca, a study conducted in South Korea showed.

The study, published Monday, 26, involved 499 volunteers – all health professionals. About 100 people received the vaccine combination, 200 received Pfizer’s two doses, and 199 were inoculated with two injections from AstraZeneca.

All subjects showed neutralizing antibodies that prevent the virus from entering cells and replicating. The result of the mixed vaccination regimen showed similar levels of neutralizing antibodies in the group of subjects who received two doses of Pfizer.

A British study published in June showed results similar to those of the Korean research – a dose of AstraZeneca followed by Pfizer produced the best T-cell responses and a higher antibody response than Pfizer followed by AstraZeneca.

The data support the decision by Brazilian states and the Ministry of Health to offer the second dose of Pfizer to pregnant women vaccinated with AstraZeneca. Last week, the steward recommended pregnant women take the second dose of Pfizer. The state of Rio de Janeiro has already been vaccinated in this way, and São Paulo will start this Tuesday, 27.

The Korean Disease Control and Prevention Agency (KDCA) reported that the research also analyzed the neutralizing effect of vaccines against variants of the new coronavirus. None of the groups showed reduced neutralizing activity against the alpha variant. However, against the eta, gamma, and delta variants, neutralizing activity was reduced by 2.5 to 6-fold.

In another study published in the New England Journal of Medicine, two doses of AstraZeneca or Pfizer were effective against the delta variant. The variant first identified in India is the most transmissible of the strains already cataloged by the World Health Organization. Still, there are no data to suggest it causes more severe cases of Covid-19.

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