Coronavirus, the rush to vaccine may actually delay the target


Although it may seem counterintuitive, proceeding slowly and not running can lead us to the finish faster, developing a safe and effective vaccine against Covid-19. This is because this avoids some problems already encountered in trials on other vaccines

(photo: chinaphotographer via Getty Images)

Those who go slowly go well and go far, says the well-known proverb. A saying that could also be applied to the search for a new one vaccine against the coronavirus, which we all want as soon as possible, but without renouncing all the necessary guarantees that it is safe and effective. The technical time for the development of a vaccine is on average long, from 12 to 18 months, and we would all like to shorten them to return to normal as soon as possible. But we must not forget that these times are necessary and that you cannot skip the mandatory steps of experimentation. Otherwise, people could risk getting more harm than good. It explains it well Douglas Green in an editorial on Science Advances, titled “Sars-Cov2 vaccines: Slow is fast” (“Vaccines against Sars-Cov-2: slow means fast”), in which the publisher remembers – it is always good to repeat it – the importance of not being in a hurry and the essentiality of having all the scientific evidence.

From safety to effectiveness

To date, the vaccine seems to be the best way to contain the epidemic and get to end of the Covid-19 pandemic. The only alternatives to date, Green points out, would be test very widespread in the population, contact tracing rigorous or effective therapy (which we don’t have for now).

They are currently under study 95 potential vaccines against Covid-19 and someone has already shown that it can produce an immune response through neutralizing antibodies that attack the virus. But this does not imply that safety is confirmed and that a vaccine showing this potential is ready for large-scale development. Furthermore, even when there is evidence that the body develops these antibodies, this result does not necessarily indicate that the vaccine is fully effective against the virus, as the Chinese researchers who have just achieved good results, in phase 1, with the vaccine pointed out Ad5-nCov against Sars-Cov-2.

An effect to avoid

It is necessary to study all the strengths but also the potential safety criticalities of a vaccine. In general, a vaccine stimulates the production of neutralizing antibodies, which attack and block the pathogen, and so-called antibodies bind, which bind to the microorganism and which, a bit like a sort of label, signal its presence to other cells of the immune system, which will then hit it. But these antibodies can also attach to other cells of the human body e sometimes damage them, for example by promoting their infection.

This phenomenon has been observed in some trials of vaccines against dengue, L’HivEbola and feline coronavirus, which is different from Sars-Cov-2. In these cases, which are highlighted thanks to the experimentation and before the vaccine reaches the person, a vaccinated individual can contract a more severe infection compared to what he would have had in the absence of vaccination. This is because the antibodies induced by the vaccine bind both to the viral particles and – and should not – to the receptors of the immune cells: in this way, in practice, they bridge the virus and these cells and promote infection. Fortunately, this phenomenon does not necessarily manifest itself and there is already a vaccine against Sars-Cov-2, tested on primates, which has excluded its presence.

Testing a vaccine

Testing a vaccine follows the same steps as testing a new drug. After preclinical testing, on animals, there is that clinic, which is divided into three stages. In the first, which involves dozens or usually at most 100 people, the goal is to provide a first demonstration of the safety and tolerability of a drug, in order to then proceed. In the second, extended to more people, we begin to study the activity of the drug and its ability to produce thedesired effect. In the third, the largest (about tens of thousands of people), we aim at confirm efficacy and safety.

The timing of the development of a vaccine can be long, usually 12 to 18 months, but sometimes even much more. For this reason, in particular situations, such as the Covid-19 emergency, the health authorities, always choosing on the basis of a benefit that outweighs the risk, can allow to shorten the time with which we move from preclinical to clinical trials or allow more people to be involved in the early stages of the trial. In this regard, the World Health Organization (WHO) has recently disclosed new ethical criteria to think of “speeded up” clinical trials but which respect the essential and necessary canons of experimentation, always in the perspective of those who go slowly go healthy and go far.

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