Sinovac Clinical Trials Halted in Brazil Due to Severe Adverse Event

In early September, the AstraZeneca/Oxford vaccine trials were put on temporary hold across all international testing sites due to a volunteer developing an unexplained illness and died. Similarly, Anvisa, Brazil's National Health Surveillance Agency, just recently suspended Sinovac's phase three clinical trials after a volunteer experienced a severe adverse event (SAE).

The only details Anvisa announced was that the incident occurred on October 29. Meanwhile, Sinovac clarified that after communicating with Butanan Institute, their partner in Brazil, it is believed that the SAE is not related to the vaccine and they remain "confident in the safety of the vaccine." No further details have been released yet.

Sinovac's vaccine candidate, CoronaVac, is one of the few vaccines around the world that is in the final stage of clinical trials. Other trails are being held in Turkey, Bangladesh, Serbia, Pakistan, Indonesia, United Arab Emirates, Bahrain, Peru, Morocco, Argentina, and Jordan. There are also four testing sites in China and nearly all of the company's employees have received the vaccine.

CoronaVac Clinical Trials

During the second phase of clinical trials, 600 healthy adults received two injections of two doses or a placebo. The most-reported complaint, the authors wrote, was pain at the injection site. Out of nearly 50,000 volunteers in China, the most serious side effects included loss of appetite, fever, fatigue, and headache. Results showed that the two-dose vaccine had good immunogenicity or induced neutralizing antibodies.

The vaccine was developed using the same technology Sinovac used to create vaccines for hepatitis, swine flu, avian flu, and enterovirus 71 (causing hand, foot, and mouth disease) that have already been approved. CoronaVac is made from an inactivated version of SARS-CoV-2. Aside from the coronavirus vaccine, they have also developed a Sabin-strain inactivated polio vaccine, pneumococcal polysaccharides vaccine, and the quadrivalent influenza vaccine.

Sao Paulo Governor Joao Doria said that among all of the vaccine candidates tested in the country, "CoronaVac is the safest, the one with the best and most promising rates." Sinovac is also one of the few companies with published results and received approval to include minors (ages three to 17) in clinical trials.

Dimas Covas of the Butanan Institute agreed with the governor saying that CoronaVac is the safest vaccine not only in Brazil but in the entire world in terms of side effects. Brazil's trails include 9,000 volunteers since September. Nearly one-third of the volunteers complained only of pain at the injection site, headache, or fatigue.

China's Leading Companies

In October, China joined the Covid-19 Vaccine Global Access (COVAX), an international alliance promising to produce millions of safe vaccine doses for developing countries. SinoVac pledged to provide Brazil up to 60 million of the two-dose vaccine supposedly by the end of this month and an additional 40 million doses to Indonesia by 2021.

Currently, despite ongoing trials, CoronaVac is already available in China for $60. Other leading Chinese pharmaceutical companies include SinoPharm and CanSino Biologics.

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