A staff member collects sample to check the condition of Vero cell culture at the COVID-19 vaccine stock solution workshop in trial operation at Sinovac Life Sciences Co., Ltd. in Beijing, capital of China, July 15, 2020. 

In late 2019, the novel coronavirus emerged and rapidly spread across the world. Tens of millions of people have been infected. Scientists isolated the virus from patients and named the virus COVID-19. As the coronavirus wreaks havoc on the world, vaccine has become a hope for humanity to conquer the pandemic. Scientists cultivated the virus at Vero cells and selected a toxic strain suitable for making COVID-19 vaccine, namely CZ strain. By far, many people have been inoculated with inactivated vaccines against the virus. 

Here are some detailed production processes of China's inactivated COVID-19 vaccine. The production of the inactivated vaccine contains six steps: cultivation, inactivation, purification, formulation, filling and packaging. The first step is to replicate large amounts of coronavirus. Scientists inject the virus into an airtight bioreactor full of Vero cells which are isolated from African Green Monkey kidney cells. Continuous Vero lineage cells can be replicated through many cycles of division and not become senescent. The coronavirus replicates itself rapidly in Vero cell culture. Those viruses are then sent through an airtight pipe into another bioreactor in which a kind of inactivator is used for inactivation. Hours later, viruses totally lose pathogenicity and the ability to replicate. They become a pool of inactivated viruses. The inactivated virus pool is then taken to the purification zone where the inactivator and other impurities will be removed. The leftover is vaccine stock solution. The stock solution will then be mixed with adjuvant and diluent at an appropriate proportion. The mixture is called a semi-finished product, which will be stored in cold storage for further examination. The product will be filled into vials or prefilled syringes at sterile environment for convenient use. Light inspection is followed to ensure vaccines are fit for use. The qualified products are then labeled with names and numbers before being packed into boxes with user guide. From cell cultivation to packaging, an inactivated COVID-19 vaccine needs 48 days to be produced. The vaccine must be stored at a temperature of 2-8 degrees Celsius. So cold-chain vehicles will be used to transport vaccines to different parts of the world.