By Jesús Pérez Gil, Department of Biochemistry and Molecular Biology, Faculty of Biological Sciences, Complutense University of Madrid.
The COVID-19 vaccination campaign has been made possible by a massive scientific effort to develop several vaccines in record time, which must now continue with the global distribution and administration of hundreds of millions of doses. However, it has also raised concerns among some people, who seem worried that they may not have all the necessary guarantees.
They argue that this requires extended safety and protective efficacy trials in several stages, over much longer periods of time. The benefit, in terms of global health, of widespread vaccine application is undeniable. This is despite the reluctance of small groups of people encouraged by messages with dubious scientific basis circulating on the internet.
The vaccines considered safest (flu, MMR) have an incidence of serious adverse effects of 1 or 2 cases per million inhabitants, and this does not invalidate their protective nature, which has been widely demonstrated. It is true that they have been tested on real populations for decades. In contrast, the new COVID-19 vaccines have only had the opportunity to be tested on the thousands of people who have participated in clinical trials, in controlled environments. These trials are essential to draw conclusions about the validity of any treatment being tested, and to ensure that these conclusions are not masked by the inevitable heterogeneity of cases in the real world.
It is the lack of its widespread application, among the millions of individuals who much better represent the real structure of the population, that makes a certain uncertainty inevitable, which can only be cleared up after years of application and analysis. The question is what balance between risk and benefit can be considered acceptable given the current circumstances.
In medicine, the process of introducing new treatments begins with approval from regulatory agencies. These agencies must ensure that all necessary studies and trials to assess safety and efficacy have been properly conducted. Once a treatment is approved and available in clinical practice, physicians carefully evaluate the balance between risks and benefits, always adhering to the principle of "first, do no harm." However, in the current context, this analysis is incomplete without also considering essential public health criteria. A global analysis for a global problem.
When assessing the likelihood of adverse effects in an individual, the impact on each person undergoing treatment is evaluated, weighing the risks of the procedure against the potential benefit. In the case of the impact of COVID-19, this also means considering the impact of not preventing infection in the general population, represented by each individual who is not vaccinated. Every person who is not vaccinated, even if their risk of contracting COVID-19 is low, puts everyone else at risk. This includes not only the most vulnerable segment of the population (who could be protected if they were vaccinated), but the entire population. This includes people whose vulnerability is not even fully understood because we still lack knowledge of many of the factors that account for the enormous differences in susceptibility to the most severe form of the disease. The fundamental difference between COVID-19 and other diseases caused by infectious agents is that we do not yet have baseline defenses against a novel virus.
The result is becoming clear: an unchecked spread of the infection to the entire global population, adding further risks that increase with each passing day without vaccination. The probability of variations and mutations appearing in strains that could evade vaccine-provided immunity is ever-increasing. This is the law of large numbers, as microbiologists well know. Furthermore, the viral loads and population incidence of the SARS-CoV-2 virus are currently nothing like those of the agents that cause influenza or other diseases with which we have long coexisted.
Our world is now completely interconnected on a global scale. This allows any viral variant that evades natural or vaccination-induced immunity to spread rapidly. This falls squarely within the purview of epidemiology and public health, and it is crucial to clearly explain the arguments in this area so that people consider population-based arguments, not just those related to personal health. It is understandable that people prioritize their personal risk/benefit over the collective benefit. Therefore, it is essential to reinforce this collective aspect when communicating the importance of vaccines.
Another argument in favor of mass vaccination comes from biology. A recently published study has determined that there are more than 1,000 species of coronaviruses similar to SARS-CoV-2 in bats. Each of these is capable of triggering another pandemic if it crosses the species threshold and certain conditions are met. If we replace bats with other species, much less is known about the coronaviruses or other viruses that could use them as hosts. For example, the pet population is comparable to the human population in size, but it is not studied to the same extent because its importance is secondary compared to human health. With a human population harboring such a massive number of viruses as the current one, the probability that any of these viruses originating from animals will recombine with SARS-CoV-2 and ultimately generate a new species or strain increases.
Geneticists and microbial ecologists could explain this very well. Hence the idea of One Health , which this health crisis is bringing to the forefront more than ever. Human, animal, and environmental health are one and the same . This is the fundamental reason why it is urgent to act to reduce the spread of SARS-CoV-2 infection worldwide, including in countries without resources. This may be even more urgent than vaccination in our developed countries, which are well-protected by enviable baseline health conditions. Where are these cross-species interactions most likely to occur? One can imagine it if one considers the images we have seen from markets where people and animals coexist seamlessly. Assessments must therefore also incorporate sociological and political factors. It would also be wise to listen to philosophers and their perspectives on the ethical and moral issues that must be considered when prioritizing political actions relevant to our area of expertise. We must also more publicly defend the value of the guarantees provided by drug regulatory agencies. The urgency and shortened timelines in vaccine development have not come at the expense of disregarding the protocols we have established for developing safe drugs. The guidelines issued by these agencies are safe (and rightly so) from ulterior motives driven solely by economic interests.
There is a certain level of uncertainty that will only dissipate as the vaccination process progresses, as has happened with all vaccines from their inception to their widespread adoption. But the procedures that have now allowed vaccines to be developed in record time are more potent, efficient, and safer than ever before. This is especially true in contexts like the current one, where an unprecedented investment of resources has been made. Science and research today are nothing like they were twenty years ago. Penicillin would not have been approved back then if the strict protocols that now define whether a drug or treatment is safe had been applied. We are talking about acting on a global scale with the maximum safety that current conditions allow. The urgency of halting the progress of the pandemic, its consequences, and its cost in lives demands it.
When opinion polls reveal enormous public doubts, it is crucial that our media outlets become fully involved in explaining the collective and epidemiological concepts at stake in coronavirus vaccination. This is not about bombarding people with information, so that the indigestion of not being able to assimilate it makes them resistant to anything that doesn't align with what they want to believe, in a blind denial of the magnitude of the problem.