Background A fully quantitative picture of national effectiveness in controlling the spread of the Covid19 virus should consider the percentage of a population vaccinated in relation to the percentage of a population as active cases . Results Mean European V ratio increased from January 11 2021 onwards; inverse correlation was found between V ratio and R statistic (p <0.001, r2=0.15, df=234). Initial threshold V ratio of 10-15 resulted in an R statistic of 1.0 or lower; this threshold increased to 30-40 with further vaccinations . Variation between countries in the V ratio increased with time . This quantitative assessment and use of a summary data-derived threshold index showed the integrated effectiveness of vaccinations and social measures for European countries for Covid19 . It established a threshold range for an R value of 1 and calculation of the number of vaccinations needed in Europe to reduce the infectivity of the virus to unity . Results can be used to quantify the relation between transmission following vaccination and social measures to control the spread of Covid19.