On December 8, 2020, in the early hours of the morning, Margaret Keenan, a 90-year-old Briton, became the first person to benefit from a specially designed vaccine against Covid-19 – outside of clinical trials. Since then, many countries have launched their own vaccination campaign in order to curb the pandemic on their territory and draw a way out of the crisis.

In France, after a continuous acceleration until the summer, the campaign has slowed down sharply in recent weeks due to the hesitation and skepticism of part of the population as to the effectiveness and safety of current vaccines – since the Emmanuel Macron’s announcements extending the use of the health pass, the pace of vaccination has resumed at an unprecedented pace. To these concerns and questions, many teams of scientists have tried to respond by studying their real effects, by following and studying in particular very large cohorts (sometimes entire populations) which make it possible to measure the impact with great precision. vaccination. And after more than seven months of vaccination, the lessons are numerous.

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  1. What can we say about the real effectiveness of current vaccines?
  2. Are they resistant to SARS-CoV-2 variants?
  3. How long does the immune protection provided last?
  4. What have we learned from their actual or potential side effects?
  5. Can side effects occur long after vaccination?

1. What can be said about the real effectiveness of current vaccines?

In April 2020, the World Health Organization (WHO) had set a minimum target of 50% efficiency for vaccines in development against Covid-19, while specifying that an efficiency of 70% would be preferable. After 3.54 billion doses injected around the world, we now have numerous observations which confirm that the vaccines distributed today have clearly exceeded these objectives.

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BNT162b2 vaccine designed by Pfizer-BioNTech is overall the one with the most positive results. In the most solid study, published in May 2021 in The Lancet, which followed a cohort of 1.65 million people in Israel, the researchers conclude that it is 95.3% effective for SARS-CoV-2 infection, 97.2% for avoiding hospitalizations and 96.7% to avoid deaths in vaccinees who received their second dose for at least seven days. The effectiveness is even higher when waiting at least fourteen days after the injection of the second dose, since it reaches 98.1% to avoid deaths due to Covid-19. The study was also carried out when the B.1.1.7 variant (known as the Alpha variant, discovered in England), which is more contagious and causes more serious forms, made up 95% of new cases in Israel.

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