Health World’s ‘best’ vaccines could soon come to poor countries -By Vishnu /11/5/21 In the 6 months since Covid vaccines became available, those based on mRNA technology have scored top marks. So far, there are only two – made by Pfizer and Moderna – and both show 95% efficacy. Other types of vaccines are usually 80% or less efficacious. This difference affects not only the protection you get as an individual but also the protection available to the ‘herd’ or society. With a better vaccine a country can reach ‘herd immunity’ faster by vaccinating fewer people. But mRNA vaccines are still confined to the rich world. This is partly because supply is limited and those countries placed their orders first. Another reason is these vaccines get spoilt if they are not stored at extremely cold temperatures. The Pfizer shot initially required storage at -80°C. Poor countries couldn’t afford to buy specialised freezers for it in bulk. A fragile molecule Why do mRNA vaccines need ultra-cold stora