Cruising or not?
Less well-known is the investigation, which is currently still in the pre-print stage, i.e. not yet reviewed by professional colleagues. US researchers compared how homozygous (three times the same vaccine) and heterogeneous (double the same vaccine, once a different vaccine) boosters differed in about 460 people. Result: the homologous enhancer increased neutralizing antibodies by 4.2 to 20 times, while the heterogeneous enhancer increased antibodies by 6.2 to 76 times. Both vaccine mixing and maintenance were well tolerated. Individuals who received a single dose of Johnson & Johnson and a booster of Moderna had an approximately 76-fold increase in antibody levels in 15 days. On the other hand, when people received a second dose of Johnson & Johnson, there was only a fourfold increase. Boosting with Biontech/Pfizer also increased antibodies more than Johnson & Johnson itself, but not as much as Moderna.
Cross vaccinations often lead to a stronger immune response. We know this from the development of influenza or HIV vaccines. With regard to two mRNA vaccines, I don’t see many differences in terms of using the same mRNA vaccine or a different one,” Kramer emphasizes. The discrepancy between the two exists, but it is small. The question is what its consequences actually are.
For Ursula Wiedermann-Schmidt, president of the NIG, there is currently no scientific data to support mixing the two mRNA vaccines. “The data on two mRNA vaccines is very good, they provide very strong and very stable vaccination protection.” It currently only recommends heterogeneous vaccination for people who have been vaccinated for the first time with the Astra Zeneca or Johnson & Johnson vaccines. You should receive an mRNA booster. In the USA, the FDA is currently advising whether to allow a “mix-and-match” approach, i.e. cross-vaccination. This depends not only on efficacy considerations, but also on logistical considerations – if vaccines can be mixed, there is more flexibility in distribution.
It is not currently regulated whether a third vaccine can be chosen in Austria. “I would not welcome doing that. It is not immunologically necessary to choose a vaccine – both mRNA vaccines are available and both are very good,” says Federmann-Schmidt.
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