Homologous or heterologous anti-Covid vaccination? These are the two roads on which many Italians under 60 have been fought, vaccinated at the first dose with AstraZeneca, then directed by a new recommendation towards the second dose with mRna vaccine. Today a new study offers a further contribution to better understand the value of the two alternatives. The novelty of the work, signed by German researchers and published in ‘The Lancet’, is that this time it is compared heterologous and homologous with respect to the neutralization capacity of the Delta variant of Sars-CoV-2. Result: “The robust inhibition of variants including the Delta variant – the authors write – further supports heterologous vaccination“.
Experts point out that it is a small job. But they add: “If confirmed in a large study, our data also support “the option of a third dose” heterologous booster for people who have completed the homologous vaccination course “with AstraZeneca when” humoral immunity is waning and patients become susceptible to infection “.
In the study, scientists from Hannover Medical School and Leibniz Institute for Primate Research in Göttingen analyzed plasma from vaccinated with AstraZeneca after homologous and heterologous booster with Pfizer, to evaluate and compare neutralizing activity against variants of concern, including Delta. The mean interval between the two doses was 73.5 days and did not differ between the two groups analyzed.
The pseudotyped virus test based on the vesicular stomatitis virus was used to assess neutralization. The mean of anti-Spike IgG antibodies was higher in vaccinated with heterologous than in those with homologous. The vaccinated with the mix also reached an adequate value in terms of the rate of neutralizing antibodies against all variants, including the Delta. The mean anti-Spike IgG antibody means correlated highly significantly with the value of the neutralization titers against the Delta variant in both groups.
The German study is a confirmation. In fact, before this work, the authors recall, it had already been demonstrated (based on the first results of a phase 2 study from Spain and further observational studies) that “robust immune responses accompanied by acceptable reactogenicity” were observed after vaccination. heterologous with AstraZeneca at the first dose and an mRna vaccine (Pfizer or Moderna) at the second. It was also “shown that heterologous booster” with Pfizer “induces higher specific T cell counts” against the virus’s Spike protein, and “high titers of neutralizing antibodies against the three variants Alpha, Beta and Gamma”.