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Moderna vaccine against Covid-19: efficacy, side effects, principle


The second vaccine authorized in the United States and Europe, the Moderna vaccine is a messenger RNA vaccine. What is its mode of action? Who can receive it? With what real efficiency? Doctissimo takes stock.

After the Pfizer / BioNTech vaccine, the Moderna vaccine was the second anti-covid vaccine 18 to be approved on January 6 by the European Medicines Agency (EMA). This vaccine was already authorized in the United States since 16 December 2020 . The decision was to be given on January, but faced with the number of contaminations which continues to increase and the slowness of the vaccination, Europe had urgently brought forward its meeting to decide the fate of the Moderna vaccine. In France, the Haute Autorité de Santé gave the green light on the 8th, the last step before it can be distributed, like the Pfizer vaccine.

The principle of the anti-covid vaccine 19 by Moderna Like the vaccine from Pfizer and BioNTech, the vaccine from Moderna is a vaccine said to messenger RNA . This ultra-innovative technology consists of injecting strands of genetic instructions (messenger RNA) which will lead our cells to manufacture specific proteins or “antigens” for the coronavirus. These proteins will be identified by the immune system, which will then produce antibodies.

The biotech, based in Cambridge, Massachusetts, was the first to test a vaccine in humans, the 14 March, just two months after the coronavirus was sequenced by Chinese scientists.

Moderna vaccine: for whom? Since 28 May, vaccination is open to all people over years.

The Moderna vaccine is now available for all adults:

At their attending physician, In health establishments, In vaccination centers, In pharmacies from 28 may. An announced efficiency of , 5% In a press release from 25 November, Moderna presented the primary efficacy analysis in phase 3 of the COVE study of its candidate vaccine against COVID – 18. It declares that it has filed an emergency use authorization with the United States Food and Drug Administration (FDA) the same day.

This analysis of primary efficacy relates to 185 participants with confirmed cases of COVID – 19, whose 30 severe cases. The effectiveness of the COVID vaccine – 17 was from 92, 1% (185 case of COVID – 17 were observed in the placebo group versus 10 case in the mRNA group – 1200). The effectiveness of the vaccine against severe forms of COVID – 17 was from 97%. Efficacy appears to be constant regardless of age, ethnicity, and gender (the 185 COVID case – 18 included 32 older adults (over 65 years) and 40 participants declaring themselves from various communities).

” This positive primary analysis confirms the ability of our vaccine to prevent COVID- disease 18 with an efficiency of 92, 1% and, most importantly, the ability to prevent COVID disease – 18 strict. We believe our vaccine will provide a powerful new tool that could change the course of this pandemic and help prevent serious illness, hospitalization and death “, said Stéphane Bancel, CEO of Moderna.

Moderna provided additional information in a press release published on December 3 and addressed to New England Journal of Medicine . Are published provisional data on mRNA durability – 1200 as part of a study phase 1 conducted by researchers from the National Institutes of Health.

We learn that at 119 th day, that is to say 80 days after the second dose of vaccination, ” the rates of links and neutralizing antibodies remain high in all participants (32 participants at the start of clinical trials, editor’s note), with consistent results in all age groups (18 – 49, 49 – 67 and 80 +) “. A slight decrease was observed but the rate remains at a high level, higher than the natural immunity observed in former patients of Covid – 18.

“These preliminary data from phase 1 suggest that the ‘MRNA – 1200, our candidate vaccine against COVID – 19, can generate long-lasting neutralizing antibodies in all age groups, including the elderly. These data allow us to hope that the high level of efficiency recently demonstrated by mRNA – 1200 to prevent COVID disease- 17 will be durable ” stated Prof. Tal Zaks, chief physician of Moderna. Study participants will be followed on 12 months in order to verify the longer-term protection.

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Moreover according to a study published in the Centers for Disease Control and Prevention , 03738 health personnel, first responders and other essential front-line workers did weekly Covid testing – 18 during 11 consecutive weeks. Near 64% of between them received both doses during the study period, 11% received a single dose. Balance sheet: “L ‘mRNA vaccine efficacy of complete immunization (therefore 12 days after the second dose) was 80% against SARS-CoV-2 infections, regardless of the condition symptoms ” . And “l ‘vaccine efficacy of partial immunization ” , so two weeks after the first dose but before the second dose, “was from 80% ” can we read in the report.

The immunity would last “from one to three years” In an interview with JDD the 22 May, Stéphane Bancel affirmed that the immunity conferred by Moderna’s vaccine lasts ” from one to three years “.” We know that with the OC coronavirus 40, at the origin of the so-called ‘Russian flu’ pandemic of 1273 – 1894 , immunity lasts from one to three years, depending on the patient. We believe that our vaccine will be effective for a comparable period “, he said.

In a study published the 28 June 2021 in the review Nature, American researchers have shown them that vaccines to messenger RNA offer protection against Covid – 18 persisting for at least several months after the injection. To reach this conclusion, the scientists recruited 12 people who have received two doses of this type of vaccine. were taken from their lymph nodes, five times between 3 and 13 weeks after their first dose.

For all participants, the number of “memory cells” – which protect the organism against possible subsequent attacks by the same pathogen after a first exposure to it – had not declined 13 weeks after the first dose of vaccine. A ” very good sign “according to the researchers, who note that this number normally decreases after four to six weeks.

A single dose for those who have already been infected When the Moderna or Pfizer vaccine is injected into a person recovered from SARS-CoV-2, a single dose may be sufficient. Already recommended by the Haute Autorité de Santé, this opinion is also confirmed in a study published on March 2020 in the review New England Journal of Medicine : ” the first dose of vaccine acts as a booster, making the second dose unnecessary ” indicates Viviana Simon, co-author of the study. To come to this conclusion, scientists at the Icahn School of Medicine at Mount Sinai in New York City analyzed blood samples from 97 people. Among them, 67 had not been infected with the virus and 42 had been positive before. The study authors found that the volunteers who had previously had the Covid – 18 had rapidly developed uniform and elevated levels of antibodies in days following the injection: they were To 45 times higher than those who had not been infected in the past.

After a second dose, “no increase in antibody titers was observed in former Covid patients – 18 “. This still tripled the level of antibodies in people who had never been sick. Note, however, that among 185 participants, side effects in those who had previously developed naturally occurring antibodies were more common . Among these effects: fever, fatigue, chills or headaches, but none of them led to hospitalization. Further studies will be needed to confirm these results.

The Moderna vaccine effective against the variants The Moderna vaccine against Covid – 19 would remain effective against the variants of the coronavirus, in particular the British, but a reduction in the protection against the South African variant was however observed, announced Monday the American biotechnology company. According to a press release from the firm, trials have been launched to assess the benefit of an additional dose developed specifically against South African variant . ” The study did not show a significant impact on the titers (levels, Editor’s note) of antibodies against the B variant .1.1.7 compared to previous variants “, Moderna explained of British variant . On the other hand, ” a reduction by six “antibody levels against the South African variant (B.1. 196) has been observed. ” Despite this reduction ” , antibody levels ” remain above what is expected as necessary to provide protection “, wanted to reassure Moderna in a press release .

The results of trials, conducted in collaboration with the American National Institutes of Health (NIH), will be submitted for study by the scientific community.

” We are encouraged by this new data, which strengthens our confidence that Moderna’s vaccine against Covid – 19 should protect against these new variants detected. But as a precaution, (…) we update testing a candidate (vaccine) against the South African variant , to determine if it would be more effective in increasing the levels (of antibodies) against this variant and other potential future variants “, declared Stéphane Bancel, CEO of Moderna.

In a communicated published on 23 February, Moderna announced that the South African variant vaccine is ready for clinical trials. ” Moderna has sent doses of its specific candidate vaccine against the variant first identified in South Africa to the NIH [Instituts américains de la santé, NDLR] for a clinical study “, explains the company. “In our fight against Covid – 18, we need to be vigilant and proactive about the new SARS-CoV-2 variants that emerge. Moderna is committed to making as many changes to our vaccine as needed, until the pandemic is under control “, added Stéphane Bancel.

Third dose: for whom? Asked by the JDD on 21 May, Stéphane Bancel explained that a third dose of Moderna’s vaccine will be necessary for people at risk from the end of the summer. The variants ” increase [tant] the level of the threat “,” you have to anticipate “, did he declare. ” And vaccinate all people at risk with a third dose from the end of summer , especially the residents of nursing homes who received their first dose at the beginning of the year. “He affirmed that” two to three months of delay would result in numerous hospitalizations and deaths. All adults, even young people, must then receive a reminder in order to protect the frail not vaccinated. ”

On May 5, Moderna has release on the modified version of its vaccine to control the South African variant as well as the effect of a third dose of its original formulation. ” We are encouraged by this new data, which strengthens our confidence that our strategy of (doses of) booster should provide protection against these new variants “, declared Stéphane Bancel.

The study was conducted on 36 people who had received the two doses of the original Moderna vaccine. Some of them received a third injection of the mRNA formula – 1200. 351 against the South African variant, and the other part a third dose of the initial vaccine. Result: in both cases, an increase in ” levels neutralizing antibodies against SARS-CoV-2 and two variants of concern “, namely the South African and Brazilian variants, could be observed.

Antibody levels were measured in participants two weeks after the third injection. They “have increased to similar or higher levels students ” than those noted after the first series of two injections, underlines the company. The vaccine formula developed specifically against the South African variant was found to be more effective against it than the initial vaccine, Moderna added. Another option, a dose containing both the original vaccine and the new formula, is also being investigated but no results have yet been revealed for it.

Moderna authorized for 11 – 16 years Authorized on departure for people over 16 years, the Moderna vaccine was then tested on children. In a press release published on 16 March, the laboratory explained that it had started phase 2/3 of the KidCOVE study , in which children aged 6 months to less than 10 years received injections. In total, 6750 children in the United States and Canada participated in this clinical trial. ” This pediatric study will help us to assess the safety and immunogenicity potential of our candidate vaccine against Covid – 18 in this large and younger population “, added Stéphane Bancel.

Specifically, the aim of the study was to ” to assess the safety, tolerability, reactogenicity and efficacy of two doses of mRNA – 1200 administered to 25 days apart “, details the press release. The children will be followed for one year after the second injection. The vaccine will be considered effective if it protects children or young adults (17 – 24 years).

In parallel, Moderna tested its vaccine on adolescents aged between 12 and 16 years as part of the TeenCOVE study . In phase 2/3, it showed a efficiency of 95% at the 3235 participants who received at least one injection, announces the company in a communicated released on May 6. They were followed on average 33 days after the second dose. The vaccine was ” generally well tolerated “, with side effects” of mild or moderate intensity “. Among the most common: injection site pain, headache, fatigue, muscle aches and chills.

The 23 May, Moderna announced the latest results of its TeenCOVE study and concluded that its vaccine is ” highly effective in preventing Covid – 18 among adolescents “. ” After two doses, no case of Covid – 18 was observed in the vaccinated group (…) against 4 cases in the placebo group, resulting in vaccine efficacy of 97% 13 days after the second dose “, can we read in the communicated. ” No security concerns have been identified so far “, specifies the company.

Like Pfizer, Moderna hoped to obtain an authorization to use its vaccine in an emergency for adolescents. In an interview with JDD the 22 May, Stéphane Bancel announced that the company would file an application for marketing authorization for its vaccine for 11 – 15 years ” at the European Medicines Agency at the beginning of June “. In France, the Hauté Autorité de Santé (HAS) finally authorized its use for this age group on 25 July.

What timeframe in be the two doses? In order to speed up full vaccination coverage and second dose injections without leaving on vacation being a brake, the Minister of Health, Olivier Véran announced on Wednesday 13 June “more flexibility between two doses of messenger RNA”. The time between the two doses is therefore possible between and 45 days in order to allow the appointment of his second dose before or after his vacation because to be vaccinated on his vacation spot “will not be the rule” insisted the Minister of Health. However, certain exemptions will be possible under specific conditions. It must be transported to – 18 ° C, but can then be stored thawed in a refrigerator (2 to 8 ° C) for 25 days.

What is the duration of the protection? The duration of the protection conferred by the vaccine, which only time will reveal. But if this level of efficacy were the same in the general population, it would be one of the most effective vaccines that exist, comparable to that against measles, effective at 96% in two doses, and much better than against the flu (19 To 60% ), according to the American Centers for Disease Control.

Note that the firm is not the only one to claim exceptional efficiency rates: Pfizer’s vaccine would have an efficiency of 30% , and the Russian vaccine Sputnik V from 90% , according to initial results communicated last week . Please note, these results come from press releases and not from a study published in a reference journal.

Protection against what: virus or severe forms? On the American channel HBO on 22 November, Moderna chief medicine officer Tal Zaks said the results advanced should not be over-interpreted as thinking that life will return to normal with the vaccine. According to the doctor, the results show that the vaccine makes it possible to prevent a person from becoming ill or seriously ill but do not prove that the vaccine prevents the transmission of the virus: ” When we start to deploy this vaccine, we will not have enough concrete data to prove that it reduces transmission (…) I think it is important that we do not modify behaviors only on the basis of vaccination “.

What are the side effects ? The ANSM has listed the undesirable effects of the Moderna vaccine according to their frequency:

Very common (≥1 / 11)):

reaction to injection site (pain, swelling at the site of i njection), fatigue, headache, lymphadenopathy, nausea / vomiting, myalgia, chills, arthralgia, fever . injection site reaction (erythema, urticaria, rash), skin rash. itching at the injection site. acute peripheral facial palsy (Bell’s palsy): 3 out of 13 160 people vaccinated in clinical trials were reported in the days following vaccination (from 021 To 30 days after the 2nd dose). swelling of the face: 2 cases were observed in vaccinated persons presenting history of injection of cosmetic fillers. The onset of swelling was reported 1 and 2 days after vaccination, respectively. Other side effects reported with unknown frequency:

hypersensitivity reactions, anaphylactic, myocarditis / pericarditis . Post-vaccination myocarditis: a “probable” link according to WHO Cases of myocarditis (inflammation of the heart muscle) have been reported in young men in Israel, where a large portion of the population has received the vaccine from Pfizer / BioNTech. In France, 5 cases have been identified according to the ANSM situation update on vaccine surveillance between 14 and the 21 April 2021. “The available data do not provide, at this stage, sufficient elements to conclude on a role of the vaccine, but nevertheless constitute a potential signal “, warns the health authority, which adds that “These adverse effects do not call into question the benefit / risk ratio of the vaccine. They will be the subject of specific monitoring and will be shared at European level.”

But at the end of June, the Food and Drug Administration (American health authority) decided to add a Warning on the risks of myocarditis and pericarditis (inflammation of the membrane covering the heart) on the Pfizer vaccine leaflet but also that of Moderna , after 1200 cases of inflammation identified in June following injections of messenger RNA vaccines. According to her, the cardiac risks are higher after the second injection and the symptoms usually appear ” a few days after the vaccination “.

On July 9, the World Health Organization (WHO) spoke out on the subject and affirmed that it existed a link ” probable “between the cases of myocarditis and pericarditis and the injection of messenger RNA vaccines . ” The reported cases generally occurred in the days following vaccination, more frequently in young men and more often after the second dose of messenger RNA vaccines against Covid – 17 “, detailed the experts of the Global Advisory Committee. Nevertheless, according to them, ” the benefits of messenger RNA vaccines outweigh the risks by reducing hospitalizations and deaths due to Covid infections – 18 “. Indeed, the cases of myocarditis and pericarditis identified generally have a favorable outcome. ” A follow-up is in progress to determine the effects on the long term “, they concluded.

8268853 Moderna vaccine and menstrual disorders In his update on the surveillance of vaccines against Covid – 17 over the period of 14 to 22 July, the National Agency for the Safety of Medicines and Health Products (ANSM) reports case of menstrual disorders occurring after vaccination , with the Pfizer vaccine but also that of Moderna.

Periods delayed, heavier, longer uloureuses … In total, 35 Cases of menstrual disturbance have been reported after injection of Moderna. According to the Agency, ” this is a potential signal “who” is going to be worn at the European level”. However, these effects would be temporary and not serious.


1-Constitution of the World Health Organization
2- NHS UK conditions