Sinovac: “CoronaVac” as an inactivated vaccine against Corona

The coronavirus pandemic required the rapid and safe development of vaccines against SARS-CoV-2. Various mRNA and vector vaccines, a protein-based vaccine and an inactivated whole virus vaccine against COVID-19 have been approved in the EU. More vaccines are in the starting blocks. This also includes the inactivated vaccine called CoronaVac from the Chinese manufacturer Sinovac Biotech, which could also be used in Germany. According to previous studies, what is the approval status, and how effective is the vaccine?

Sinovac’s inactivated coronavirus vaccine is awaiting approval.

The rolling review of the coronavirus vaccine CoronaVac has been running since May 2021. The European Medicines Agency (EMA) checks and evaluates initial data from the Chinese pharmaceutical manufacturer Sinovac before the official application for approval. The level of knowledge gained through this early examination should later accelerate the approval process. Vaccination reactions and possible side effects of the vaccine are also intensively examined as part of the rolling review.

In some countries such as Turkey, Chile, Brazil, and Indonesia, the vaccine has already received emergency approval and is already used in the fight against coronavirus. CoronaVac has already received conditional approval in China. The World Health Organization (WHO) also recommended the vaccine as part of the COVAX vaccine distribution program.

 

Inactivated vaccine against Corona: This is how CoronaVac works

The mode of action of the first approved vaccines is based on the so-called spike protein of the coronavirus. This is responsible for the “docking” of the virus cells in the human body. The blueprint for this virus protein is isolated and gets into the body with the help of vector or mRNA vaccines that have been approved. This then begins to replicate the spike protein itself using the blueprint. The immune system recognizes the protein as a foreign body and produces antibodies and T cells against the pathogen. In this way, the immune system is trained in the event of a later coronavirus infection.

Sinovac’s corona vaccine, on the other hand, is based on a different but already known technology: the rendered harmless (inactivated) virus is injected into the body as an inactivated vaccine, producing antibodies and T cells. The way the vaccine works is similar to Valneva ‘s vaccine, which has also been approved in Europe.

CoronaVac is manufactured as follows:

1. The virus is first multiplied in cell cultures, so-called Vero cells.
2. Then, the Vero cells are cleaned and inactivated using a chemical compound called beta-propiolactone.
3. Aluminium hydroxide is added as an adjuvant. An adjuvant is an auxiliary substance in inactivated vaccines to enhance the vaccination effect.

The inactivated virus is recognized as a foreign body when a person receives the vaccine. The immune system begins to produce antibodies and helper cells. The vaccinated person, therefore, has an acquired immune response: If the person later comes into contact with the coronavirus, the immune system recognizes the virus as foreign and begins to defend itself against it.

Vaccination with CoronaVac is given in two doses two to four weeks apart. The vaccine can be stored at refrigerator temperature.

How effective is the Sinovac vaccine?

The company says the vaccine protects 79 per cent against severe coronacourses. On the other hand, initial studies attribute the vaccine’s effectiveness to between 50 and 90 per cent. A phase III study from Turkey found an effectiveness of 83.5 per cent against symptomatic courses. In a large-scale study from Chile, this protective effect was given as 65.9 per cent. Vaccination is intended to prevent severe courses better.

 Several studies have shown that the protective effect is significantly lower than mRNA vaccines or the vector vaccine from AstraZeneca . Vaccination protection should also be significantly reduced against the omicron variant. Even after three doses of the inactivated vaccine, the vaccinated persons did not have sufficient antibodies against omicron. Sufficient antibodies could be detected if a booster from BioNTech/Pfizer was used instead for the third vaccination.

 

What side effects are there?

The data from the phase II/III studies also indicate comparatively few side effects, which could be milder than the vaccines approved. Possible side effects include pain at the injection site, tiredness, muscle, headache or joint pain. Serious side effects have not been observed to date.

Inactivated vaccines: A proven technology

Although inactivated vaccines are among the older types of vaccines, they are generally no less effective. Vaccination protection can be more comprehensive and apply to mutations since the vaccine contains the complete virus. Another advantage is the comparatively fast effectiveness: Since the body does not have to produce the spike protein first, the protective effect can theoretically take effect earlier.

However, their disadvantage is that the protective effect wears off more quickly than live vaccines, so regular boosters are necessary.

Inactivated vaccines are already being used in Germany to protect against other diseases, including vaccines against diphtheria, polio, whooping cough, rabies, TBE, tetanus and Hib (Haemophilus influenzae type b).

More inactivated vaccines against Corona

CoronaVac is not the only dead vaccine against the coronavirus. With BBIBP-CorV and WIBP-CorV from Sinopharm, two other inactivated vaccines from China are currently used in different countries. There is also the Indian coronavirus vaccine BBV152, which is also based on this technology.

The European manufacturer Valneva has also developed an inactivated vaccine against Corona that has already been approved in the EU. Likewise, the vaccine from the manufacturer Novavax is sometimes counted among the dead vaccines, although it is not a vaccine of this type but a recombinant protein vaccine.