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AstraZeneca and Pfizer: vaccination combination works stronger – ten times more antibodies – study

AstraZeneca and Pfizer: vaccination combination works stronger - ten times more antibodies - study
Photo by Alisha Jucevic/Bloomberg via Getty Images

Strong booster: If the first vaccination with Astrazeneca as a second dose of Pfizer follows, the immune response is stronger than with two identical vaccines, as a German study has now confirmed.

Accordingly, the vaccinated after such a vaccine combination produced ten times more antibodies and a stronger T-cell reaction than after two doses of AstraZeneca. This confirms the strong effectiveness of such heterologous vaccinations.

In Germany, four vaccines are currently used against the Sars-CoV-2 coronavirus: the two vector vaccines based on carrier viruses from AstraZeneca and Johnson & Johnson and two mRNA vaccines from Moderna and Pfizer. 

Since it has been known, however, that cerebral vein thrombosis can occur in rare cases and especially in younger women after vaccination with the vector vaccines, many people who have been vaccinated for the first time with AstraZeneca receive an mRNA vaccine as a second dose.

Advantage through heterologous vaccination?

As early as May 2021, several studies from Spain and Great Britain, among others, suggested that such a vaccine combination – also called heterologous vaccination by immunologists – could even increase the vaccine effect. The problem with vector vaccines is that the immune system also forms antibodies against the carrier virus after the first dose. This immune response then weakens the effectiveness of the second dose of vaccine.

This problem does not exist with heterologous vaccination: because the mRNA vaccine does not use a carrier virus, the second dose retains its full effectiveness. A team led by Martina Sester from Saarlandes University has investigated how this actually works with a combination of AstraZeneca as the first dose and Pfizer as the second dose. 

Two weeks after the second vaccination, they determined the immune reaction in 250 people who had received either the vaccine combination or a double dose of AstraZeneca or Pfizer.

“We not only examined how many antibodies they had formed against the coronavirus in the vaccinated people, but we also determined the strength of the so-called neutralizing antibodies. This tells us how well the antibodies keep the virus from entering Cells to invade,” explains Sester. The team also determined the cellular immune response by the T cells.

Ten times more antibodies and more T cells

The result: the analysis of the antibody formation showed that a combined vaccination, as well as a double Pfizer vaccination, showed significantly higher effectiveness than a double AstraZeneca vaccination. In the first two variants, about ten times more antibodies could be detected in the blood. 

“With the neutralizing antibodies, the combined vaccination strategy showed even slightly better results than a double pfizer vaccination,” reports Sester.

The same was found in the T-cell-mediated immune reaction: Here, too, the vaccination effect was strongest for the heterologous vaccination and the double mRNA vaccination. 

“This shows quite clearly that the double Astrazeneca vaccination is less able to mobilize the immune system than the other two variants,” explains Sester. 

“That does not mean that many of the people who have been vaccinated in this way do not have adequate vaccination protection. However, a second dose can no longer achieve the full potential that is actually in this vaccine.”

A sensible strategy – also for a third vaccination?

Even if the researchers have not yet been able to fully evaluate all the data on cell formation, they were, according to their own statements, surprised by the clarity of the results. 

“This is also the reason why we want to share this with the public now and have not waited first for the scientific review process,” says Sester. 

For the scientific publication, the researchers will now evaluate their data more precisely under various aspects, such as gender and age and the question of which vaccine combination occurred with the most side effects.

According to the research team, the results already show that the combination of vector and mRNA vaccines can be beneficial. 

“In addition, it would be important for people with previous illnesses whose immune defense is weakened by drugs, for example, to check whether they should not receive a combined version as the third vaccination at the latest in order to generate the body’s immune response as broadly as possible,” says Sester.

Photo by Alisha Jucevic/Bloomberg via Getty Images