mRNA, such as those developed by Pfizer and Moderna, are highly effective and quick to develop, they are expensive to make and must be stored at very low temperatures.For the Pfizer vaccine, this entails storage in a special freezer at a temperature between –80 and –60°C (-112 and -76°F).Pfizer and Moderna also recommend that their respective vaccines are injected in two doses several weeks apart to maximize their efficacy.These factors present challenges for low and middle income countries.
Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.Conventional vaccines that are based on inactivated, weakened, or genetically modified viruses can be highly.