You hesitate to get vaccinated against Covid-19? Here are our answers to your questions

Since Monday, May 31, 2021, all French people over 18 are now eligible for vaccination. The opportunity – unexpected a year ago – to get rid of Covid-19 or, at the very least, to make SARS-CoV-2 a benign virus circulating only slightly … provided that at least 70% of the population received two doses of the vaccine. But at the time of making an appointment to be vaccinated, without opposition in principle irrational and despite the more than two billion doses administered in the world, legitimate doubts may still persist, it is human. Here are the answers to the most common questions that “vaccine-hesitant” may ask themselves when choosing their niche.

1) Weren’t vaccines developed too quickly to ensure their safety?

In principle, the development of a vaccine takes several years. This time, it took less than a year between the discovery of a new pathogen, the SARS-CoV-2 coronavirus, and the development of the first unprecedented vaccines. Yet, surprising as it may seem, both safety and efficacy have been tested in accordance with the rules of clinical trials. That is to say in three successive phases: the first observing the toxicity of the injection on a small number of patients, the second evaluating the immunological response of another group of patients, the third testing on a large scale the vaccine effectiveness in more than 30,000 people for Moderna with the US National Institutes of Health and more than 40,000 people for the Pfizer laboratory. On this clinical aspect, the difference with the classic process is to have made the different stages overlap. Instead of waiting for the final results of each phase before organizing the next, the protocols and recruitment of the three phases were launched at the same time.

In addition, statistically significant results in phase 3 were obtained very quickly because the vaccines were preferably tested in countries where the virus was circulating the most when the trials were launched. In fact, the more widely a virus circulates, the shorter the time needed to obtain efficacy results from a vaccine.

As Sciences and the Future explained in a previous survey, most of the time saved was thanks to logistical and financial risk taking, historic cooperation between laboratories, governments and health authorities, as well as pharaonic resources invested.

Finally, to be reassured, we can also say that since the vaccines were put on the market, the trials have not stopped, since a sort of “phase 4” of pharmacovigilance is also carried out by the health authorities. This enabled the rapid detection of serious but very rare side effects such as venous thrombosis with the AstraZeneca vaccine. As of June 3, nearly 24 million doses of the Pfizer vaccine have been administered in France, for 20,987 cases of adverse effects (0.09%).

2) Messenger RNA technology is too recent. Isn’t it better to have vector vaccines like those from AstraZeneca or Janssen?

Attention has focused on the technological innovation of mRNA vaccines. Rightly so: the least that can be said is that the method shows promise in many therapeutic areas. However, this focus overshadowed the fact that the viral vector used by AstraZeneca and Janssen – an adenovirus – was also never the subject of a marketing authorization before these two Covid vaccines. The technology of the viral vector to present the vaccine antigen has admittedly been used for a long time, but no vaccine using an adenovirus as a vector has so far been deployed on a very large scale. And it turns out that both efficacy and safety mRNA vaccines are superior to adenovirus vaccines.

3) How can you be sure that the vaccines will not have a long-term effect?

After more than eighteen months of a pandemic that has already killed between 3.6 and 6.9 million people, the long-term effects of even an asymptomatic SARS-CoV-2 infection are just as unknown. A viral infection can indeed have long-term consequences: play a role in triggering autoimmune diseases in predisposed people or cause the appearance of cancer years later as is the case with human papillomaviruses, for example. , the main cause of cervical cancer.

As for vaccines, however, no long-term effects have ever been documented. Adverse effects, whether mild or serious, have always been detected in the first weeks or months after vaccination. And if we have in mind the controversies surrounding autism and the measles-mumps-rubella vaccine or multiple sclerosis allegedly triggered by the hepatitis B vaccine … we must get rid of it for good: these links have been scientifically invalidated for many years now.

MRNA has no reason to depart from the rule: the molecule is very fragile as evidenced by its storage conditions which require an extremely low temperature. Once injected, the mRNA is read by the cell and immediately destroyed. Everything suggests that the potential adverse effects are triggered by the establishment of the specific immunity sought, before the system stabilizes.

The trace left in the body by a virus capable of replicating itself and of interfering in all kinds of tissues and organs is much more worrying, as evidenced by these patients with “long Covid” affected by persistent symptoms during months, including those who did not initially develop severe infection. The vaccine only mimics the infection with a copy of a small part of the virus, a single protein.

4) Does it really protect against infection?

No vaccine provides 100% protection for 100% of a given population. But the mRNAs developed against Covid appear to be much more effective in preventing infection than many other vaccines before them. Once the two doses are administered, they prevent nearly 95% of symptomatic cases. That is, infection is still possible in rare cases, but it will probably go unnoticed and, most importantly, prevent severe forms of the disease. In addition, analysis of data from a study conducted by the Israeli Ministry of Health and Pfizer showed as early as March 2021 that the vaccine reduced the risk of asymptomatic infection by 89.4% once the two doses were received.

It should be remembered that so far, only vaccines against smallpox (a disease eradicated by vaccination) and measles are considered “sterilizing”, that is to say, completely preventing the entry of the pathogen into the body. ‘organization. This does not mean, however, that the ten or so other mandatory in children, for example, do not have a major effect on the circulation of these diseases (rubella, diphtheria, tetanus, polio, hepatitis B, pneumococcus, etc.) .

5) Does it really prevent transmission?

Long pending, this question is now better understood: as Sciences and the Future wrote in March 2021, monitoring the millions of people who have received the two doses of an mRNA vaccine now makes it possible to estimate the reduction in the risk of transmitting the virus at 75% to 90%. In Israel, which served as a giant laboratory for Pfizer due to a mass vaccination campaign, researchers have shown that in the few infected “12 days or more after vaccination show a significant reduction in viral loads, potentially affecting excretion and contagiousness”. In summary, while vaccine blocking of infection and transmission of the virus is not foolproof, it is at the very least very effective. Getting vaccinated is therefore a major step in breaking the chains of transmission and preventing the virus from circulating.

6) What is the benefit of vaccination for a young and healthy adult who does not present a priori no serious risk factor?

First, there is the general interest. Or the satisfaction of knowing that we can hardly contribute to the circulation of a virus that could end up affecting people who are not eligible for vaccination: immunocompromised patients or those with allergies, the main contraindications to vaccines. At the individual level, the benefit may seem lower. However, in view of the risks of the vaccine and those of even a mild infection, the benefit is statistically always in favor of the vaccine. Because it is not known what predisposes a healthy young person to develop a severe infection or to have symptoms that persist for months. “Long Covid” also greatly affects young people in good health. Not vaccinated until proven guilty.

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