Published data on phase 1 and phase 2 clinical trials reports that the most common side-effect of the Sinovac vaccine is pain at the site of the injection, which is also common with other available COVID-19 vaccines. According to the World Health Organization’s information on the safety of this vaccine, this is the only side-effect that is related to the vaccine with certainty. Other mild side effects have been reported such as headache, fatigue and muscle pain, which resolved after two days, and researchers noted that they occurred in both the study group that took the vaccine, as well as the group that took the placebo (did not receive the vaccine for comparison). The studies also reported a lower chance of developing fever as a side-effect of this vaccine when compared to other COVID-19 vaccines. 

Six healthcare workers in Thailand took Sinovac’s vaccine and showed stroke-like symptoms. All six have recovered after being given stroke treatment, and additionally no blood clots were found when examining them further. Experts were not able to explain why these patients experienced these symptoms. 

According to The Strategic Advisory Group of Experts (SAGE) continued monitoring following authorization is recommended to continue to assess the safety of this vaccine. Among the observed potential severe side-effects of this vaccine are a severe allergic reaction known as Anaphylactic shock, a disorder causing inflammation of small blood vessels known as Henoch-Schönlein purpura, facial paralysis, and cerebral haemorrhage (bleeding in the brain), and a rare neurological disorder called acute disseminated encephalomyelitis. One participant in a clinical trial studying the Sinovac vaccine experienced a blood clot. However, a link between the occurrence of these conditions and the vaccine is yet to be established, meaning there is not evidence that shows these events are more than coincidental, rather than caused by the vaccine. More research and monitoring is needed. 

SAGE reported that they are “moderately” confident in the low risk of serious side effects after two doses in adults. They reported being less confident in the risk for older adults, based on the currently available data.

SAGE is in charge of advising the World Health Organization on multiple global health issues among which are matters of immunization. SAGE currently recommends the use of Sinovac for individuals 18 years of age and older, including pregnant women, to prevent severe illness and hospitalization due to SARS-CoV-2 infection. The vaccine is considered safe in the age groups between 18 and 59 years, however more evidence is needed about its safety in individuals who are 60 years and older. Due to the small number of individuals in that age group in the clinical trials, there is currently not enough data to suggest whether the vaccine is safe or not. The current recommendation is for the vaccine to be administered in two doses, two to four weeks apart. 

Data from studies conducted in Brazil and Chile have shown that the vaccines offer less protection in individuals older than 60 with a greater decrease in immunity following the vaccination compared to ages 18 to 59. The current recommendation for a booster dose is to follow for the second dose by six months, and should be guided by the WHO Prioritization Roadmap. 

Sinovac-CoronaVac vaccine is produced by Sinovac Biotech, pharmaceutical company based in China. This vaccine is intended to be an opportunity to increase supply of vaccines to developing countries that do not have access to the same vaccines developed in the United States by Moderna and Pfizer. 

In January 2021, initial research from Brazil reported that this vaccine was 78% effective. An announcement followed one week later reducing this result to slightly above 50%. This remains over the benchmark set by the World Health Organization to determine if a vaccine is effective for general use.

The vaccine was validated for emergency use by the World Health Organization on the first of June, and as of June 9th, it has been accepted for use in 26 countries around the world. Early recipients of this vaccine included Indonesia, where the president received the vaccine on live television to kick off a national vaccination campaign. 

Data from a study in Brazil showed that individuals who received two doses of Sinovac’s shot were half as likely to develop symptomatic disease, and none of them developed severe disease or were hospitalized due to COVID-19. Additional data from Indonesia and Turkey shows 65% and 83% protection against symptomatic COVID-19 respectively. Official reports of the vaccine’s protection are based on its ability to prevent moderate and severe symptoms, however the data reported from the study in Brazil did not report on a group in the study that was classified to have “very mild” infection despite having been vaccinated. This creates a gap in the bigger picture of the level of protection provided by this vaccine. 

There is currently not enough data to support using Sinovac-CoronaVac interchangeably with other available COVID-19 vaccines, and the recommendation is to take two doses of this same vaccine to achieve the desired protection. 

There is currently not enough information about the vaccine’s effect on transmission of the virus.