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The effectiveness of vaccination in Israel

By the 3rd April 2021, SARS-CoV-2 had infected 131 million people and caused 2,8 million deaths worldwide. In Israel, it had been responsible for 82 1748 infections and 6 236 deaths. The Pfizer-BioNTech vaccine, based on mRNA technology was authorised in Israel from December 2020. The health ministry launched an unprecedented vaccination campaign, with the aim of administering two doses of the vaccine to the country’s 6,5 million inhavitants aged over 16 (71% of the population).

By the 3rd April 2021, 61% of inhabitants had received a first dose, a proportion never attained elsewhere. According to clinical studies, the Pfizer-BioNTech vaccine gives 95% protection against symptomatic forms of COVID-19 7 days after the 2nd injection in people aged over 16. Israeli researchers have recently published results of this large-scale vaccination campaign which, due to its size, has allowed study of categories that have been little analysed before, such as effects on elderly people. The effectiveness of the Pfizer-BioNTech vaccine has thus been confirmed.

The researchers analysed the country’s epidemiological surveillance data from the 24th of January to the 3rd of April 2021. The campaign began in Israel on the 20th of December 2020, a period when infections were rising, leading to a lockdown from the 27th of the same month. By the 3rd of April, 72% of people aged over 16 and 90% of over-65s had received 2 doses of the vaccine. During the period studied, there were more than 200 000 infections by SARS-CoV-2 (66% in people aged over 16), more than 7 000 hospitalisations, more than 4 000 severe cases of the illness and over 1 000 deaths. Of cases of SARS-CoV-2 in the over-16s, 71% were in non-vaccinated individuals and only 4% in people having received 2 doses. Taking all the data into account, researchers were able to calculate that the vaccine was 91% effective in blocking infection by the virus and 97% effective in preventing symptomatic forms of the illness.

The researchers were also able to confirm the vaccine’s effectiveness against the illness in elderly people. For example, in people aged over 75, it was 97% effective. They were also able to show that the vaccine’s protective capacities were only moderate after a first dose, thus underlining the importance of being fully vaccinated.

In addition, they observed that, as vaccination levels increased, the overall number of cases of SARS-CoV-2 infection went down. During the period in question, the UK variant was estimated to be dominant at 95% of all strains. It seems therefore that the Pfizer-BioNTech vaccine is also effective against this variant.

However, the effectiveness of the vaccine against the South African strain, another variant under close surveillance which had already appeared in Israel, could not be analysed due to the small number of total cases. The massive and rapid vaccination campaign in Israel was an opportunity to study the effectiveness of the Pfizer-BioNTech vaccine on a national scale, with an estimation of herd immunity of at least 60%. The vaccine seems to be effective after 2 doses, even in elderly people (a previously little studied section of the population) and against the UK variant as well.

However, it remains to be seen how long protection against COVID-19 will last, and whether the emergence of new variants enable the virus to escape immune responses activated by the vaccine.

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