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Why is there no coronavirus vaccine yet?

May 18, 2020

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This story originally appeared in The Conversation

Why is there no coronavirus vaccine yet?
Why is there no coronavirus vaccine yet?

By Martina Bécares Palacios, Autonomous University of Madrid

In these days when the number of people affected by COVID-19 continues to increase and even the ice palace in Madrid had to be converted into a mortuary to temporarily hold the coffins of the victims of the capital, this is a recurring problem We all ask ourselves: How long will it take for the vaccine to end the pandemic? A question that can be extended to other infectious diseases such as Ebola, malaria or AIDS, which it has been fighting for a long time and which still do not have an effective vaccine.

Developing a vaccine is a complex process. First of all, previous knowledge of the biological and immunological properties of the pathogen – virus, bacteria or parasites – must be available. The next step would be to synthesize the candidate vaccine and run tests to assess its effectiveness. If the previous steps were successful, all legal requirements must be met when they are placed on the market.

In a way, the process can be compared to a war against the pathogen, which requires a careful strategy to achieve the final victory.

Know the enemy

Throughout evolution, pathogens have developed several weapons and strategies to escape the host’s immune response – ours. Sometimes they have proteins that allow them to suppress the immune system, or cheat him This causes our body to develop ineffective reactions. In other cases, their strategy is based on a constant mutation capacity, which enables them to escape our defenses again and again, as is the case with the influenza virus.

A detailed knowledge of the biology of the pathogen, the structure of its proteins and the clinical properties of the associated disease have a decisive influence on the success of the vaccine. In cases such as the one in question, in which the opponent we are dealing with is new, previous studies on similar microorganisms may be essential.

Choose where you want to aim

The choice of the antigen or antigens, ie the pathogen proteins contained in the vaccine, is an essential aspect when designing the attack strategy.

In the 18th century Edward Jenner laid the foundation for vaccination with an entire microorganism as an immunogen and led to one of the great milestones in medicine, the eradication of smallpox. However, this strategy is not possible or safe for all infectious diseases, and there are different types of vaccines today.

The so-called “subunit vaccines” are currently being introduced, in which choose an antigen from the pathogen against which the reaction is to be directed. This choice is not easy because it is a fundamentally empirical process: although there are some tools to predict the immunogenicity of a molecule and it is good to know the pathogen well, you always have to prove what works and what does not .

An additional complication is that the recipe The vaccine also contains adjuvant compounds that favor induction of a stronger response to the antigen. Choosing the right combination of antigen and adjuvant requires testing. And that means time, which is very valuable in situations like today.

Evaluate the strategy

Once the attack strategy has been selected, it must be checked whether it is effective. To do this, it must first be tested on animals. First, the induction of the immune response is then evaluated Flat tire The prototype of the vaccine in the experimental animal examines the type of immune response induced and its ability to neutralize the hostile microorganism.

In order to be able to assess the results, you should have previous knowledge that correlates the immunological parameters measured in the laboratory with the degree of protection granted to the patient. This implies data from patients who have overcome the disease. And again it takes time.

Another option is to have animal models that develop the disease pierce them the vaccine and evaluate protection against subsequent inoculation of the pathogen. These animal models of diseases are extremely useful, but their development requires effort and, of course, more time.

First small battles, then war

Once animal testing is done, it’s time to assess human safety and efficacy: clinical trials. The safety of the vaccine candidate is first assessed in a small group of healthy volunteers – phase I studies – and then transferred to larger groups in which the appropriate doses and guidelines are tested – phase II.

If all goes well, the effectiveness of the vaccine in an even larger number of people – Phase III – will be assessed. After this process, the vaccine can be made. And it has to be done in reasonable quantities and ensure the high quality and legality standards required by the pharmaceutical industry. Every step must be approved by the relevant authorities to ensure everyone’s safety.

In emergency situations like today, these tests can of course be accelerated. But certainly not as much as we would like, since we must not forget that they form a chain: if we skip one step, we are more likely to fail in the next.

Although the saying goes that Zamora was not won in an hour, it was won in the end. The same applies to the development of vaccines: although in situations like the current one the apparent slowness of the process can be frustrating, it can be done with time and effort. Just have a look at our vaccination calendar.The conversation

Martina Bécares Palacios, postdoc and honorary professor in the Department of Preventive Medicine, Public Health and Microbiology at the Autonomous University of Madrid

This article is republished by The Conversation under a Creative Commons license. Read the original article.