Which combination of COVID vaccines is better at protecting against coronavirus?
Various combinations of coronavirus vaccines increase the body’s immune response to coronavirus.
AstraZeneca and Moderna or Novavax coronavirus vaccine combinations produce much higher levels of neutralizing antibodies and T cells than the Swedish-British mono vaccine.
Scientists looked at the data of 1,070 British people who were injected with one dose of the vaccine AstraZeneca or Pfizer, then nine weeks later they were injected with either a similar drug, or the development of Moderna or Novavax, to see how they did.
“Just because you’ve received dose one of a particular vaccine, doesn’t mean you have to receive the same vaccine for dose two,” said Matthew Snape, professor at Oxford University.
The study found that AstraZeneca vaccine recipients had 17 times more neutralizing antibodies than those who got two doses of the AstraZeneca vaccine. Novavax vaccine recipients had four times more neutralizing antibodies than those who got two doses of the AstraZeneca vaccine.
For people who started with the Pfizer jab, getting a second dose of the Moderna vaccines jab led to 1.3 times as many neutralizing antibodies as two doses of Pfizer. Getting Novavax as the second jab led to 20% fewer antibodies.
The study, which was published in the Lancet, also found that T-cell responses were different when different types of vaccines were used together.
Pfizer and Moderna jabs are both mRNA-based vaccines. They deliver a small piece of genetic code called messenger RNA to human cells, telling them how to make the coronavirus spike protein on their own. Viral vector vaccines, like the AstraZeneca jab, do the same thing, but they use a harmless virus to deliver these instructions. Protein-based vaccines, like the Novavax jab, deliver pre-made fragments of the spike protein along with an immune-stimulating agent.
While two doses of either the AstraZeneca or Pfizer vaccine led to the same number of T-cells, combining the AstraZeneca vaccine with a second dose of Moderna led to 3.5 times more T-cells than if they were given alone. After a second dose of Novavax, there were four and a half times as many T-cells.
After first shot of the Pfizer jab, a second dose of Moderna led to 1.5 times more T-cells, but a second dose of Novavax led to fewer T-cells.
“It tells us that the RNA and the viral vector vaccines are doing something quite different when it comes to priming for the T-cell response,” says Snape.
It had been thought that combining different viral vector vaccines, like the Ebola vaccine, could lead to better immune responses, but this is the first time this has been proven.
“What was a bit more surprising is that we didn’t see that so well with the RNA vaccines – especially when it comes to the T-cell response, adds Snape.
“RNA followed by a protein (Novavax) was slightly underwhelming when it came to the T-cell response.”
The study also looked at how the different vaccine combinations worked against the Delta and Beta variants of the virus. T-cell responses didn’t go down much, but there was a drop in neutralizing antibodies in all of them.
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