The effect of strict lock down measures on Covid-19 seroprevalence rate and herd immunity

BackgroundCovid-19 seroprevalence rates and serological tests are important tools in understanding the epidemiology of the disease and help in the fight against it. Seroprevalence rates vary according to the population studied and the test employed and they range from 0.133 to 25.7%. The purpose of this study is to assess the seroprevalence rate in a population of healthy blood donors living under strict lockdown measures in Jordan which has in total 144 confirmed cases per million population. MethodsLeft-over sera and plasma samples from 746 healthy blood donors were tested using a commercially available FDA approved kit having a sensitivity and specificity of 100% and 99.8% respectively. External positive controls were used for validation. ResultsMore than 80% of the donors were men 18-63 year old and residing in the capital city of Jordan, Amman. All tested specimens were negative yielding a zero seroprevalence rate in this healthy blood donor population. ConclusionStrict lockdown measures effectively limit intracommunity spread of the infection, however at the cost of lack of any acquired community immunity. Additionally the use of highly specific test is recommended in low prevalence setting.