Sinovac Biotech is a biopharmaceutical company that creates vaccines for infectious diseases. Sinovac's COVID-19 vaccine is called CoronaVac and it is a two-shot, inactivated virus vaccine that is currently in use in Asia, South and North America, and Europe.

An inactivated virus vaccine is considered a more traditional type of vaccine. It's made by growing parts of a virus in a lab and then killing off the virus, so it can't cause disease, but can still give people immunity.

Unlike other vaccines CoronaVac does not need to be frozen, which makes transporting and distributing it much easier. The vaccine can also stay in long-term storage for years without expiring.

Clinical trials of the vaccine showed mixed results. It appeared to be at least 80% effective at preventing a COVID-19 infection that required medical treatment and just over 90% effective at preventing hospitalization and death, when doses are given 14 days apart. However, the participants in this trial were aged 18-59 so they are not representative of entire populations. The results also did not give information about whether researchers tested trial participants for asymptomatic infections, long COVID symptoms (due to the timeframe surrounding the trials). The study also reported trial information from Brazil and Turkey despite the fact that the study also took place in Indonesia and Chile.

Later trial information from Brazil showed that the drug's efficacy at preventing symptomatic infection was 50.7%, despite interim data showing the vaccine was 65% effective.

Yet another recent study from the University of Chile showed that CoronaVac was 56.5% effective 14 days after the second doses were administered in the country, but one dose was only 3% effective.

Later reports from the company's trials in Chile noted that CoronaVac was 67% effective in preventing symptomatic infection, 85% effective in preventing hospitalization, and 80% effective in preventing deaths in real world settings. This data is notable because clinical trials from Sinovac have involved tens of thousands of participants, whereas the Chilean study involved 10.5 million people in non-controlled settings (i.e. outside of laboratories). The study also involved giving vaccine doses 28 days apart instead of just two weeks like in the clinical trials. Thus, findings on the vaccine's effectiveness have been mixed.

Sinovac Biotech said that participants who received the vaccines 21 days apart, rather than 14 days apart, had a higher level of protection.

CoronaVac has been approved for use or granted emergency use authorizations in 22 countries and is currently in seven Phase III clinical trials in different nations. The World Health Organization is expected to review CoronaVac's application for emergency use between April 26 and May 3 of 2021. This approval is a prerequisite for any vaccines being purchased through the COVAX facilities and can also give confidence in the approved vaccines to countries whose health regulatory groups are not as rigorous in their evaluations.

Despite inconsistent rates of protection given by CoronaVac potentially due to the presence of different variants in different locations, this vaccine appears to meet the WHO's 50% threshold for efficacy. This Sinovac vaccine has been administered in many countries with mixed success but continues to gain approval from national drug regulatory agencies who believe its data supports its usage. The World Health Organization will review Sinovac's application for emergency approval of the vaccine in late April or early May of 2021 which will potentially allow the vaccine to be used in dozens of more countries, partially due to its long shelf life and lack of freezing requirements.