Pfizer / BioNTech vaccine is over 95% effective against Covid-19, but the level of effectiveness drops sharply when a person only receives one of two doses, according to study in Israel, the largest ever performed in real life.
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Published in the medical journal
, this study highlights
"the public health benefits of a national vaccination program,"
according to its authors, scientists from Pfizer and the Israeli government. They note that in Israel, the world champion country for vaccination, the latter
"has been the main driver of the decline in Covid-19 infections"
. However, we must be careful in generalizing these conclusions to other nations, because the speed of vaccination programs and the evolution of the pandemic differ from country to country, they warn.
This study is the version published and reviewed by other independent scientists of the first results unveiled in March by Pfizer and the Israeli Ministry of Health.
It relates to health data collected between January 24 and April 3, when 72% of those over 16 (nearly 5 million people) and 90% of those over 65 in Israel had received their two. doses of Pfizer / BioNTech vaccine.
The analysis focuses on the efficacy of the vaccine against the English variant (called B.1.1.7), which is dominant in the country.
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The study shows that the vaccine is
in people over 16 years of age seven days after the second dose: it protects 95.3% against infections, 97.2% against hospitalizations and 96.7% against deaths. These levels of protection remain similar among those over 85. But they drop significantly when people have received only one of the two doses: 57.7% against infection, 75.7% against hospitalizations and 77% against deaths in those over 16 years of age. This study
"shows the importance of a complete vaccination in adults"
, with two doses, judge the authors. According to them, a single dose could also offer shorter protection, especially with the emergence of more resistant variants to the vaccine.
During the analysis period, there were 232,268 confirmed Covid infections in Israel (with 4,481 severe infections and 1,113 deaths), and nearly 95% of the samples tested were of the English variant. The researchers point out that this has not made it possible to study the effectiveness of the vaccine against the South African variant, also circulating in the country. In February, a first large-scale study (1.2 million people) carried out in Israel and published in the journal NEJM had reached similar conclusions.