Barely A Week Since Pfizer Inc Announced A Vaccine, Another Company Has Come Forth With A Vaccine That Is More Than 94% Effective In Preventing Covid-19 Infections. Moderna Inc Said On Monday Its Experimental Vaccine Was 94.5% Effective In Preventing Covid-19 Based On Interim Data From A Late-Stage Clinical Trial, Becoming The Second U.S. Company In A Week To Report Results That Far Exceed Expectations.But As Winnie Lubembe Reports, Health Cs Mutahi Kagwe Remains Adamant About The Effectiveness Of These Vaccines Saying Kenyans Will Not Be Used As Guinea Pigs.