Pfizer, BioNTech coronavirus vaccine shows fewer side effects

The study tested doses of each vaccine ranging from 10 micrograms to 100 micrograms. The 30-microgram dose of B2 is being taken forward in clinical trials.

With the original vaccine, called BNT162b1 or B1, patients between the ages of 18 and 55 had adverse events thought to be related to the vaccine 50 per cent of the time at the 30-microgram dose.

Those between the ages of 65 and 85 had related adverse events 16.7 per cent of the time.

For the second vaccine, BNT162b2 or B2, patients between 18 and 55 had adverse events thought to be related to the vaccine 16.7 per cent of the time, and no adverse effects thought to be related to the vaccine were reported in those between the ages of 65 and 85.

Both vaccines use mRNA - the genetic messenger the body uses to make the DNA code into proteins - packaged inside a fatty capsule, called a lipid nanoparticle, that allows it to get into cells.

The mRNA instructs cells to make a protein, which then triggers the immune system into action.

According to the report, Pfizer has said that some data from its large study of the B2 vaccine could come as early as October.