The Moderna vaccine after Pfizer or AstraZeneca provides better protection

Vaccinated individuals have a better immune response when, after receiving the first dose of the AstraZeneca or Pfizer/BioNTech vaccine, they receive the Moderna vaccine nine weeks later, according to a new British scientific study.

The researchers, led by Professor Matthew Snape of the University of Oxford, who is in charge of the large-scale “blind” and randomized Com-COV2 study on various combinations of COVID-19 vaccines—who published their findings in the medical journal *The Lancet*— according to Reuters and the British “Guardian,” analyzed data from 1,070 volunteers over the age of 50.

It was found that A second dose of Moderna following a first dose of Pfizer produces more antibodies and a stronger T-cell response than two doses of Pfizer. One dose of Novavax following Pfizer produces more antibodies than two doses of AstraZeneca, but fewer antibodies and a weaker cellular immune response compared to two doses of Pfizer. The study found, in general, that The combination of a first dose of AstraZeneca and a second dose of another vaccine produces a stronger immune response than two doses of AstraZeneca.

Neutralizing antibodies were 17 times higher in those who received Moderna after AstraZeneca and four times higher in those who received Novavax after AstraZeneca. Those who started with Pfizer and then received Moderna had 1.3 times more antibodies than those who received Pfizer again, while those who received Novavax after Pfizer had 20% fewer antibodies.

While two doses of either AstraZeneca or Pfizer produced similar T-cell counts, those who received Pfizer after AstraZeneca had 3.5 times more T cells, while those who received Novavax after AstraZeneca had 4.8 times more T cells. A second dose of Moderna following Pfizer resulted in one and a half times more T cells, while a second dose of Novavax resulted in fewer.

The new findings, like other similar ones to date, confirm that Mixing vaccines is safe and effective, which is important given that the mass administration of third doses has begun, often using different vaccines than the first two. The new study reinforces scientists’ belief that a third dose of Moderna for those who were previously fully vaccinated with AstraZeneca (which applies to a large number of people in Greece as well) will lead to high levels of neutralizing antibodies and T cells.

A previous study conducted a few days ago had shown that the Pfizer and Moderna booster shots dramatically enhance the immune response compared to the two-dose regimen (with the second vaccine having an even greater effect than the first).