Study shows that AstraZeneca vaccine third dose boosts antibodies against Omicron variant

A third AstraZeneca vaccine dose significantly increases neutralizing antibodies levels against the Ômicron variant (B.1.1.529), a new study indicates. The research was conducted independently by researchers from different institutions, including Fiocruz and Oxford University. And these results were published in preprint form on the bioRxiv platform (Omicron-B.1.1.529 leads to widespread escape from neutralizing antibody responses) on Thursday.

A third AstraZeneca vaccine dose significantly increases neutralizing antibodies levels against the Ômicron variant (Image:Peter Ilicciev)

"As we have observed, the Ômicron variant is capable of infecting people with the full vaccine regimen, as well as those who have been previously infected by other variants. The data presented in this study show that the third dose is able to increase the neutralizing antibodies against Ômicron presence [were increased by 2.7-fold after AstraZeneca's third dose], rescuing the sera neutralizing capacity from vaccinated people as observed for the other variants of concern after the second dose," explained Marco Krieger, vice president of Production and Innovation at Fiocruz.

Serum obtained from individuals one month after receiving the booster dose neutralized the Omicron variant at levels similar to those observed for Alpha and Delta variants neutralization after the second dose. For researchers at this publication, the result was considered encouraging because even in the face of this new variant challenge, it was possible to obtain a protective response.

The study analyzed blood samples from people infected with COVID-19; those vaccinated with two doses plus a booster; and those who had reported previous infection with other variants of concern. The study included samples from 41 individuals who received three doses from AstraZeneca. As pointed out in the study, "neutralizing antibodies against Omicron are strengthened after a vaccine third dose, meaning that the campaign to provide booster doses should add considerable extra protection against Omicron infection".

It is also worth noting that data from another laboratory study (Broadly neutralizing antibodies overcome SARS-CoV-2 Omicron antigenic shift) reinforce the effect of AstraZeneca against Omicron: in this case, individuals vaccinated with the two doses maintained neutralizing action against the new variant, albeit with a reduction compared to the original strain. The AstraZeneca/Fiocruz vaccine has been shown to be able to induce a diverse and long-lasting response to multiple variants.