How mRNA vaccines work
November 17, 2020 - Messenger RNA vaccines carry genetic instructions which enable a recipient’s cells to make viral proteins that prime the immune system to produce protective antibodies.
If enough antibodies bind to a virus, it can’t enter the body’s cells to replicate. Also, killer T cells recognise viral proteins displayed by virus-infected cells and tell those cells to self-destruct to keep the virus from spreading.
Now, two experimental messenger RNA (mRNA) vaccines -- one by Pfizer-BioNTech and another from Moderna -- have sparked hope of a way out of the coronavirus pandemic. Other mRNA candidates for Covid-19 are under development at CureVac in Germany and Imperial College London in the UK.
One advantage of mRNA vaccines is that they are potentially faster to develop and manufacture, and are unlikely to produce unwanted reactions from the immune system. Instead, mRNA vaccines carry a protein blueprint via so-called lipid nanoparticles into the recipient’s cells. These microscopic droplets of oily liquid are unlikely to be harmful.
On Monday (November 16) Moderna said its mRNA-1273 candidate vaccine was 94.5 per cent effective at preventing Covid based on results from extensive studies. That is similar to Pfizer-BioNTech’s preliminary results of more than 90 per cent effective.
The Pfizer-BioNTech candidate must be stored at ultra-cold temperatures at minus 70 degrees Celsius, posing significant logistical issues. By comparison, Moderna’s vaccine can be transported and stored at standard refrigerator temperatures of 2 to 8 degrees Celsius for 30 days.