The UN is doing a fantastic job grouping all the available information on the vaccines against covid that are being developed in the world. As of November 19, United Nations information says there are 132 vaccines in clinical development and 194 vaccines in preclinical development. Preclinical development refers to the period in which all the scientific evidence of a vaccine is collected in the laboratory, both in in vitro models and in animal models. The clinical phase is reached by those vaccines whose preclinical results support their being tested in people, first in small groups to evaluate their safety and then in larger groups to confirm that safety and test their efficacy.
Of all these vaccines against covid in development, only 10 have already reached phase 3 or 4 of the clinical study. In other words, only 10 vaccines have been shown to be safe and effective, have been marketed globally, and can now be evaluated for their long-term effects. And if you look at Europe, the EMA (European Medicines Agency) has only authorized the use of 4 of them, which are the ones that have been and are being put in Spain at the moment. The reason that not all vaccines that have demonstrated efficacy and safety have been approved by the EMA is that each agency has different regulations and criteria. That is why there are times when the US agency that deals with this, the FDA, approves the use of drugs that the EMA has not approved and vice versa. What is essential is that each agency follows firm criteria and that they evaluate all the data before authorizing any vaccine, and that is what is currently being done. With regard to other vaccines that are being used in other areas of the world such as Chinese, Russian or even Cuban, the reality is that the data is still not as solid as that provided by the vaccines that have been approved in the EU and Therefore, more information is needed to be able to evaluate them.
It is important to highlight that of the 132 vaccines in clinical development and the 194 in the preclinical phase, the vast majority of them use a single virus protein, the spike protein, as an immunogen. This means that all of them use the same fragment of the virus to present it to the immune system and induce a response against the virus. So, in practice, almost all of these vaccines are very similar, since they use as a robot portrait of the virus the same region of the spike that is capable of promoting a powerful protective immune response. And this was known since the beginning of the pandemic thanks to previous studies that had been carried out with other coronaviruses such as the original SARS. With the appearance of new variants of concern, some vaccines are now using the viral spike of variants different from the original one from Wuhan as a robot portrait or immunogen to better protect against those that are more frequent. This is the case of the vaccine that Hipra is testing in Spain at the moment.
The difference between vaccines does not focus, therefore, on the robot portrait used to give the alarm signal and induce an immune control against SARS-COV-2, but on the type of warning system. Thus, each type of vaccine sends the robot portrait or the viral spike to the cells of our immune system using different strategies. Just as a robot portrait of a suspect can be disseminated on social media, television, or the print media, different vaccines use different routes of dissemination. Some focus on the use of recombinant proteins or inactivated viruses, which are the most classic and are also used to combat other infections, and others focus on non-replicative viral vectors, DNA, or messenger RNA, which are the most modern but that have also been studied for decades. It is important to note that all these technologies have been known and have been studied in a very rigorous way for a long time. Each of these vaccines has its peculiarities in terms of how they should be stored, since some are very sensitive to temperature. These differences complicate its use in contexts where preserving the cold chain is more complex, such as in developing countries.
Another variation on the vaccines that are underway is how they are administered. They are mostly being designed to be injected intramuscularly, approximately 77%. But there is 6% that has been designed to be inoculated intranasally, like the one being developed in Spain by the team of Luis Enjuanes and Isabel Sola. And these are the ones that are called, with a bit of luck, to achieve a sterilizing immunity. That would mean that vaccinated people would not get it. It is still too early to know if they will succeed because they have not reached the clinical phase, but that is the main hope to finally end the pandemic.
And although it seems that there are many vaccines in the clinical development phase, the reality is that we will need many more effective vaccines against covid 19. Only in this way can we guarantee their access to the entire world population, to pass 42% of people currently vaccinated worldwide 100% safely and quickly.
Nuria Izquierdo-Useros She is a doctor in biology, head of the emerging pathogens group at IrsiCaixa.
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