When the radio rings in the mix

Corona vaccination What do we know about the vaccine combination "Mix and Match"

The "Mix and Match" procedure has been recommended by Stiko since April 1st for all under 60-year-olds who have received their first vaccination with the Astrazeneca vaccine - although there is hardly any scientific data on this. The Stiko recommendation for the combination vaccination was made after expert assessments and benefit-risk considerations. In February, the so-called Com-Cov study began in Great Britain, which examines the mixture of different vaccines during a vaccination cycle. In Germany, too, small studies are currently being carried out in Ulm and Freiburg, among others.

British study - combination vaccinations

The first data on the safety of the mix and match procedure from the British study are now available. They were published in the Lancet. According to this, the vaccine mix is ​​very safe in the short term. However, there are clear indications that the side effects after the second injection with a different vaccine are significantly stronger than when immunization is carried out with just one vaccine.

Between 60 and 80 percent of the Mix and Match vaccinees reported mild to moderate side effects after the second injection - for example headache, tiredness, muscle pain, a slight fever and general feeling of illness. The good thing about it - all of these side effects subsided within a few days and no one had to go to the hospital because of it.

There are still no results on effectiveness. However, there is hope that the mix of vaccines will increase prime-boost immunization with heterologous vaccines and even increase the breadth of immune responses. Research has been going on since the 1990s to combine different vaccine platforms with the aim of increasing the immune response. It's called heterologous prime boosting.

Heterologous vector vaccines could be more effective

In the case of vector vaccines in particular, the effectiveness can be increased if two single doses of different vector vaccines are given. This is how the Sputnik V corona vaccine works, for example, it consists of two different vectors. This combination is intended to counteract the well-known problem of vector vaccines that the body not only develops immunity against the target gene, but also against the vector itself.

And studies in Ebola and HIV research have also shown that the immune responses were better with heterologous - that is, mixed - combination of vaccines than when both vaccinations were given with one vaccine.

Advantages of the mix of mRNA and DNA vaccines?

Mixing vector vaccines like AstraZeneca and mRNA vaccines like BioNTech and Moderna could also boost our body's immune response. The background to this is that a robust immune response in the body is based on several pillars. First there are the virus-neutralizing antibodies, but then there are also the T-helper cells, which increase antibody production and, third, cytotoxic T-cells, which kill infected cells.

Because vector vaccines such as Astrazeneca activate T cells more strongly, while the mRNA vaccines from Moderna and Biontech induce a strong antibody response. The combination of the two could therefore bring great advantages. Studies in mice support this theory. In late January, researchers reported, in a publication that has not yet been reviewed by experts, that a combination of an mRNA vaccine and the Astrazeneca vaccine caused a stronger immune response in mice than either vaccine alone.

And there is evidence that a combination of vaccines can also be more effective in humans. The immune response of people is particularly high if they already had Covid-19 and then received a vaccination with Biontech or Moderna. Vaccine expert Leif-Eric Sanders from the Berlin Charité says that such a booster effect is also expected in people who receive Astrazeneca as the first vaccination and an mRNA vaccine as a second injection.