Anti-Covid vaccines, third dose, virus transmission … we disentangle the true from the false!

• Anti-covid vaccines have been brought to market too quickly, they are unreliable. FAUX

Despite the speed with which they were developed, none of the mandatory rules for the development of any drug were bypassed. These vaccines were first tested on animals. Then, in humans, through three phases including more and more people (first a few dozen, then a few hundred and finally several tens of thousands). If serious or frequent side effects had appeared in one of the three phases, the vaccine candidates would have been rejected. “Usually, research teams wait for one phase to be completed before attacking the next. For covid vaccines, given the urgency, the three phases were carried out in parallel. In addition, independent experts from the European and French medicines agencies worked in an accelerated manner in order to validate the files of several thousand pages presenting all the evidence of the harmlessness and effectiveness of these vaccines. Only then did they issue the marketing authorizations “observes Pr. Bouvet.

• Messenger RNA changes our DNA. FAUX

During the injection, the messenger RNA contained in the vaccine enters the muscle cells of the arm. “It enters cells or cytoplasm into the body. There, it delivers the information it carries: the genetic code needed to make the Spike protein (which is found on the surface of the Sars-Cov-2 virus). Ribosomes present in the cytoplasm seize it and produce this protein. The immune system recognizes it as foreign and triggers a response (manufacture of antibodies and lymphocytes). But at no time does messenger RNA enter the nucleus or modify the DNA. In just a few days after the injection, it is destroyed and therefore does not remain in the body “ insists Pr. Bouvet. Messenger RNA is of concern, because it is believed to be only recently known. In reality, it was discovered in 1961 and during the last 30 years, many researchers have taken an interest in this molecule: several dozen clinical trials have been carried out on humans, in particular for the design of various vaccines and the fight against cancer. But for lack of sufficient funding, they were moving slowly. The Covid crisis played the role of an accelerator: thanks to the huge funds released in emergency, vaccines could be developed in just a few months, on the basis of these 30 years of research.

Read also: Side effects, adjuvant, messenger RNA, booster… 8 key questions about vaccines

• The anti-covid vaccines are still in the testing phase. FALSE.

Phase 3 of the clinical trial is well and truly over. On the other hand, vaccines have now entered a phase of observation with regard to their use in the general population. Continuing to monitor them will allow us to learn more about their efficacy against variants and the duration of the immunity they grant. “We can also have a clearer vision ofpossible rare side effects. As much as it was possible to identify the most frequent during phase three of the clinical trials involving a few tens of thousands of people, we will only be able to identify the rarest in hundreds of thousands of people “explains Prof. Bouvet. This close surveillance made it possible in particular to detect very quickly the increased risk of deep thrombosis and thrombocytopenia induced by the Astra-Zeneca adenovirus vaccine in young people. “As soon as the facts were proven, the authorities reserved this vaccine for over 55s for whom the increased risk did not exist” she underlines.

• Deaths caused by messenger RNA vaccines are hidden from us. FALSE.

It seems highly improbable. “As soon as a person dies in an unexplained manner – that is to say in the absence of any known pathology and at an early age – a medical investigation is carried out to try to understand the causes of his death. The fact that she had been vaccinated against covid shortly before necessarily appears in her medical file since everything is computerized. A possible causal link will then necessarily be sought “describes Pr. Bouvet. In addition, the National Agency for the Safety of Medicines and Health Products (ANSM) has set up enhanced surveillance of anti-covid vaccines in order to analyze in real time all the declarations made by health professionals or by vaccinated persons.

• Messenger RNA vaccines are more effective than adenovirus vaccines. True and false.

The data available allow us to state that all vaccines, whether to messenger RNA (Pfizer and Moderna) or adenovirus (Astra Zeneca et Janssen), have equivalent efficacy in protecting against severe forms of the disease and hospitalizations. On the other hand, it seems that messenger RNA vaccines protect a little better against contamination by the new variants and reduce transmission “ notes Pr. Bouvet.

• Getting vaccinated does not prevent you from catching covid. TRUE.

It is indeed possible tobe infected with the covid virus even if you are vaccinated. But then it is very unlikely to develop a severe form. “It must be understood that this disease has two faces. It can take place at the level upper airways: the virus enters through the nasal mucous membranes, multiplies there and then disappears after a few days. It is then a mild or even asymptomatic form. But this disease can also occur in the lungs and it is then a more serious form. This is the one from which current vaccines protect us, but not necessarily the first. Today, one of the challenges of research is to develop vaccines that would induce immunity in the upper airways and would prevent the virus from penetrating the mucous membranes of the nose and from developing there “observes Pr. Bouvet. Thus, a vaccinated person could no longer be infected or transmit the virus. Interesting to know: at the very start of infection, the viral load is the same in a vaccinated person as in an unvaccinated person, but it drops much faster. “The duration of excretion, and therefore of contagiousness, is therefore less in the vaccinated” she concludes.

• It is better to wait for a “classic” French vaccine. FALSE.

He is probably not ready to arrive! “For now, the drug agency has no data on the efficacy and safety of this vaccine, which would be in development at Sanofi. Furthermore, 70% of the French population having already been vaccinated, it will be very complicated for the laboratory to find unvaccinated volunteers to carry out its tests. It is therefore quite likely that this classic vaccine, that is to say one containing the inactivated virus, will only be tested as a booster. To wait for it would therefore be risky “ advances Pr. Bouvet. Moreover, the “classic” vaccines already used in China and India seem to have fairly low efficacy rates, of the order of 50%.

• Mixing of vaccines is more efficient. TRUE.

When the Astra Zeneca vaccine ceased to be used for young people, it was decided to continue the vaccination protocol for those who had not had their second dose using the Pfizer vaccine or Moderna. “The results were conclusive and better immunity was obtained with the Astra then Pfizer or Moderna regimen than with two doses of Astra. This is not very surprising: insofar as Pfizer and Moderna are a little more effective than Astra Zeneca, it has broadened the spectrum of vaccination “she notes. What about the mixing between RNA vaccines messenger, for example according to a Pfizer then Moderna scheme or the reverse? For the moment, we do not have sufficiently successful studies to confirm the superiority of this “heterogeneous” vaccination scheme. the track is under study.

• A 3th dose will be essential. True and false.

The further away from the date of vaccination, the lower the antibody level. The drop in efficiency is of the order of 6% every two months. Now, it is known that the neutralization of the delta variant, in particular, requires a high level of antibodies. This is why France recommends a 3th dose of vaccine, initially to people over 80 years of age or living in nursing homes, then in a second step to people over 65 or suffering from a comorbidity “she explains. To receive a 3th dose, it must be at least 6 months from the 2th dose and not have contracted covid before or after vaccination. “Making the disease confers a longer lasting and better immunity than the vaccine. The 3th dose would therefore be useless “she adds. Certain centers should undoubtedly propose to couple the 3th dose with influenza vaccination. And the youngest, will they also be entitled to a 3th dose? To see which way the benefit / risk balance will tip, we will have to wait for more studies on the decline in their immunity to the vaccine over time and on how they might tolerate a 3th dose (they respond more to vaccination than older people). Case to follow.

With the Pr Elisabeth Bouvet, infectious disease specialist, president of the Technical Committee on Vaccinations (CTV).

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