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Is the 3rd dose of the vaccine effective? The case of Israel

After several months of calm since the beginning of 2021, Israel has now seen the arrival of a 4th wave of the COVID-19 pandemic. However, more than 55% of the population were vaccinated between 5 and 7 months ago with 2 doses of the Pfizer-BioNTech mRNA vaccine. This undoubtedly means that immunity will now be tending to diminish; in addition, the dominant Delta variant can partly escape immune responses. To combat this current wave, the Israeli government launched a campaign to administer a 3rd dose of the vaccine, with an interval of at least 5 months from the 2nd dose. Israeli researchers have been evaluating its effectiveness against the appearance of serious cases.

To do so, the researchers used data from the Israeli population. They compared more than 700 000 individuals who were vaccinated with a 3rd dose between the 30th of July and the 23rd of September 2021 to a group of the same size having received only 2 doses. The average age of participants was 52 years old. The scientists evaluated the efficacy of the 3rd dose by comparing hospitalisations, severe cases, and deaths.

The 3rd dose of the vaccine seemed to be 93% effective in respect of hospitalisations (29 admissions to hospital in the group having received 3 doses, against 231 admissions for the other group). In addition, the 3rd dose would appear to be 92% effective in preventing severe cases of COVID-19 (17 against 157) and 81% effective in preventing deaths (7 against 44). Efficacy is similar in men and women. 

In conclusion, according to vaccination data from Israel, the administration of a 3rd dose of the Pfizer-BioNTech vaccine seems to be effective against severe cases of COVID-19. Other countries, such as the United States, Germany and France, have also begun campaigns for administration of a 3rd dose of the vaccine.

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