Following AstraZeneca with Pfizer shot boosts antibody response

Giving a dose of the Pfizer/BioNTech COVID-19 vaccine four weeks after an AstraZeneca shot produces better immune responses than a second dose of AstraZeneca’s, Oxford University researchers said on Monday.

In a study of 830 older adults, mixed two-dose schedules of AstraZeneca and Pfizer vaccines produced higher concentrations of antibodies against the coronavirus that a full schedule of the AstraZeneca shot.

The most effective approach – two doses of Pfizer/BioNTech mRNA vaccine – produced levels of antibodies about 10 times higher than two doses of the AstraZeneca vaccine, the researchers reported on Friday in a Lancet preprint.

However, the AstraZeneca shot followed by a Pfizer jab induced antibody levels about as high as two Pfizer/BioNTech doses. Giving the Pfizer shot first, followed by AstraZeneca’s, was not as successful. That combination yielded antibody levels higher than two AstraZeneca shots but lower than two doses of the Pfizer vaccine.

There were no new safety issues uncovered in the study. Matthew Snape, the Oxford professor behind the trial, said the findings could be used to give flexibility to vaccine rollouts but were not significant enough to recommend a broad shift away from clinically approved schedules.

About the vaccine

What are the ingredients in the Pfizer-BioNTech COVID-19 vaccine?

The ingredients are mRNA, lipids ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2 [(polyethylene glycol)-2000]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3-phosphocholine, and cholesterol), potassium chloride, monobasic potassium phosphate, sodium chloride, dibasic sodium phosphate dihydrate, and sucrose.

How does an mRNA vaccine work?

mRNA, delivered to your body’s cells by lipid nanoparticles, instructs the cells to generate the spike protein found on the surface of the novel coronavirus that initiates infection. Instructing cells to generate the spike protein spurs an immune response, including generation of antibodies specific to the SARS-CoV-2 spike protein.

mRNA vaccines do not contain any virus particles, meaning that they don’t contain weakened or dead parts of a virus or bacterium.2

Do mRNA vaccines change a person’s DNA?

mRNA is a transient carrier of information that does not integrate into human DNA. mRNA does not enter a cell’s nucleus, which is where our DNA is kept.