The Sinovac vaccine, also known as CoronaVac, is a COVID-19 vaccine developed by the Chinese pharmaceutical company Sinovac Biotech. Its main purpose is to prevent infection from the SARS-CoV-2 virus, which causes COVID-19.
How Sinovac Works
Sinovac’s CoronaVac is an inactivated vaccine. This type of vaccine uses whole SARS-CoV-2 virus particles that have been chemically or physically inactivated. These inactivated virus particles still retain their structure, allowing the immune system to recognize them.
When the vaccine is administered, the body’s immune system encounters these inactivated virus particles. The immune cells then learn to identify the various components of the virus, including its spike and nucleocapsid proteins. This recognition triggers the production of antibodies and activates other immune responses, preparing the body to fight off the live SARS-CoV-2 virus if it encounters it in the future. The vaccine also includes an adjuvant, aluminum hydroxide, which helps to boost the immune system’s response to the inactivated virus.
Protection and Safety
Clinical trials and real-world studies show the protection offered by the Sinovac vaccine. In a large Phase 3 trial conducted in Brazil, two doses of the vaccine, given 14 days apart, showed an efficacy of 51% against symptomatic SARS-CoV-2 infection. This same trial indicated 100% efficacy against severe COVID-19 and hospitalization starting 14 days after the second dose. Real-world data from Chile, involving millions of vaccinated individuals, reported the vaccine to be 66% effective against symptomatic COVID-19, 88% effective against hospitalization, 90% effective against ICU admissions, and 86% effective against deaths.
The Sinovac vaccine is generally well-tolerated, with most reported adverse reactions being mild. Common side effects include pain at the injection site. Other mild side effects include fatigue, headache, and muscle pain. Studies have also noted a lower incidence of fever with the Sinovac vaccine compared to some other COVID-19 vaccines. Serious adverse events are rare. While isolated cases of conditions like severe allergic reactions or certain neurological disorders have been reported, a direct causal link to the vaccine has not been established.
Global Use and Approvals
The Sinovac vaccine has seen widespread adoption globally, particularly in countries across Asia, South America, and Africa. Its storage requirements, typically 2–8 °C (36–46 °F), are similar to those for flu vaccines, making it manageable for distribution, especially in low-resource settings.
The World Health Organization (WHO) granted the Sinovac-CoronaVac vaccine an Emergency Use Listing (EUL) on June 1, 2021. This listing signifies that the vaccine meets international standards for quality, safety, and efficacy, and it facilitates global procurement and distribution. The EUL also made Sinovac eligible for inclusion in the COVAX Facility, a global initiative aimed at providing equitable access to COVID-19 vaccines, particularly for lower-income countries.