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A One Step Closer to Coronavirus Immunization

A new pre-publication study released April 19, from Sinovac Biotech demonstrates that their COVID-19 vaccine is effective at protecting monkeys from coronavirus.

According to scientists for the first time, one of the many COVID-19 vaccines developed has protected an animal, Rhesus Macaques, from infection by the new coronavirus.

Macaque monkeys received three injections of a novel vaccine at medium or high dosage and were compared to control monkeys that received a placebo vaccine. These monkeys were then exposed to COVID-19 after 22 days.

Monkeys that received the vaccine showed almost no signs of the virus, while the control monkeys developed the server pneumonia and other coronavirus symptoms.

Vaccines operate by training the immune system to recognize a disease-causing agent so that the immune system will be equipped to defend against the invader if it infects the body. The body naturally develops antibodies to foreign agents it encounters, so a vaccine aims to introduce a harmless version of a virus to a person, allowing the immune system to develop the appropriate antibodies.

There are several ways vaccines work to achieve immunization. A modern approach to vaccines uses only a piece of the virus since the body doesn’t need to recognize the entire virus to develop an immune response. Vaccines of this nature can be easier to mass-produce since the proteins used in the vaccine can be expressed in fast-growing cell culture. While the production is more rapid, it can be difficult to develop a method of protein expression that is useful for immunization.

The Sinovac vaccine did not appear to cause infection in any of the monkeys that were tested, even when they were given a high dosage. There is also a danger that untested vaccines can cause the immune system to become overstimulated, leading to what is called a “cytokine storm”. The Sinovac vaccine did not appear to cause adverse immune system reactions. In fact, there was no evidence that the vaccine harmed the monkeys, which suggests the vaccine could be safe for humans.

Another concern is that monkeys do not develop the most severe symptoms that SARS-CoV-2 causes in humans. The Sinovac researchers acknowledge in the paper that “It’s still too early to define the best animal model for studying SARS-CoV-2,” but noted that unvaccinated rhesus macaques were given the virus “mimic COVID-19-like symptoms.”