Using Astrazeneca and as a second dose Biontech/Pfizer probably has no disadvantages for vaccinees in terms of efficacy and tolerability, according to a preliminary Charité evaluation. According to the study, a combination of the preparations at an interval of ten to twelve weeks is well tolerated and elicits comparable immune responses as a vaccination series with Biontech twice, wrote Charité scientist Leif Erik Sander on Twitter.

The background to the mixed vaccination series is a recommendation by the Standing Commission on Vaccination (Stiko) following the discovery of rare but severe complications following first-time Astrazeneca vaccinations, particularly in younger people.Based on risk-benefit considerations, people younger than 60 who already have an Astrazeneca vaccination are recommended to receive a second vaccination with an mRNA vaccine such as Biontech/Pfizer. However, experts still saw a lack of reliable data on safety and efficacy.

The Charité interim evaluation has been published as a so-called preprint. This means that a review by external experts and publication in a scientific journal are still pending.Sander's team collected and compared data from about 340 healthcare workers who were vaccinated between late 2020 and May 21 - including one group twice with the Biontech/Pfizer vaccine three weeks apart and another with Astrazeneca for the first vaccination and Biontech for the second.Frankfurt-based virologist Sandra Ciesek wrote on Twitter that these are "important data." She commented, "Briefly summarized: Immune response is (as expected) very good and comparable to homologous vaccination with mRNA vaccine."SPD health expert Karl Lauterbach tweeted, "This combo is well tolerated and still somewhat stronger than double BionTech vaccination. The combination can be recommended."

The researchers themselves restrict that this was not a randomized controlled trial, i.e. with random assignment of the subjects to the groups. It is unclear to what extent observed differences could also be related to the longer vaccination interval of the group with the different vaccines.The findings appear to contradict a recent Lancet study that found vaccinees with two different vaccines had an increased likelihood of mild and moderate side effects after the second dose.However, the Charité scientists point to differences in the study design, the age of the test subjects and different vaccination intervals. The longer interval between the two doses in the Berlin study could have something to do with the less pronounced vaccination reactions, they suggest.

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