Both are American companies but Pfizer is developing its vaccine in partnership with German biotech company. Pfizer, claims its vaccine is 90% effective, though, as Grindrod cautions it is far too early to say if that fiver percent difference is a true difference. One significant difference between the two is that Modera vaccine remains stable at normal vaccine storage temperatures, while the Pfizer vaccine requires ultra-low temperatures of around -70C. This requirement could present Pfizer’s vaccine with storage and transportation challenges, as the company admitted when it announced the vaccine.