Pfizer’s effectiveness goes back to 95% –

by time news
from Silvia Turin

Those who were vaccinated were 19 times less likely to have severe Covid disease than those who were vaccinated with two doses and the chance of getting infected dropped 11 times

Israel has approved since July 30 administering a third dose (recall) of the Pfizer vaccine to people of and equal to or greater than 60 years and who had received a second dose of the vaccine at least 5 months earlier. As happened in winter and summer with vaccine efficacy data, the country anticipates the future of what will happen with the vaccine (and with the third dose), even if each nation has peculiarities that influence the results and that make the data not directly and totally applicable to every reality.

The third dose to the elderly

The first third dose study in Israel was published in New England Journal of Medicine on September 15 and shows that the third dose achieves the purpose: who has been vaccinated has had 19 times less likely to have a serious illness from Covid compared to those who have been vaccinated with two doses and the likelihood of getting infected dropped 11 times. The data comes from the Israeli Ministry of Health database and concerns 1,137,804 people aged 60 and over and who had been fully vaccinated 5 months earlier, monitored over the period from 30 July to 31 August 2021. In the primary analysis, the scholars compared the rate of Covid infections and the rate of severe disease among those who received the third dose. at least 12 days before (booster group) and those who had not received the third dose but were fully vaccinated. In the secondary analysis, the infection rate 4 to 6 days after the third dose was evaluated, compared to the rate of at least 12 days after the booster.

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Effectiveness returned to 95%

The results showed that in the group vaccinated with the third dose for at least 12 days, the infection rate was 11.3 times lower, the severe disease rate was lower by a factor of 19.5. In the secondary analysis the confirmed infection rate at least 12 days after vaccination was lower than the rate after 4-6 days of a factor of 5.4. Each day during the 12 to 25 day period after receiving the third dose, the booster group had a lower confirmed infection rate than the no booster group by one factor from 7 to 20. The scholars explain that the third dose, in the presence of the Delta variant, reports the effectiveness of the vaccine among those who received the booster at about 95%, a similar value to the original vaccine efficacy reported against the Alpha variant.

The program and the unanswered questions

Israel has now extended the recall program to the entire population adult. In Italy the third dose is provided for those at risk of developing severe Covid: those with a series of pathologies (frail people) or at occupational risk (health). The administrations will start on Monday.
The question that still needs to be answered now how many months will the effect last beneficial of the third dose.

September 19, 2021 (change September 19, 2021 | 16:47)

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