A large study carried out in Israel on over 80,000 vaccinated people confirmed the decline in vaccination effectiveness. At six months, the positivity rate among the vaccinated is 15.5%
That Covid vaccines are not neutralizing and immunity decreases with the passage of time is documented by numerous studies. A research just published on theBritish Medical Journa
L conducted on 80 thousand people in Israel, one of the first countries in the world to start the vaccination campaign but which saw a resumption of infections in December 2020, confirms this trend. 7
It emerged that the Pfizer vaccine provides excellent protection in the first few weeks after vaccination, but the risk of contagion for vaccinated in all age groups begins to increase 90 days after the second dose and it grows more and more as time goes by.
The results
The study was carried out by researchers from Leumit Health Services and is based on the examination of electronic medical records of 83,057 adults (mean age 44 years) who between May and September underwent a molecular swab at least three weeks after the second dose of vaccine and who had never previously shown signs of SarsCoV2 infection. Those who had contracted Covid before the study and those who had already received the third dose of the vaccine were excluded.
The results show that 7,973 participants (9.6% of the total) tested positive for the swab, almost all with Delta variant. The analysis shows that, after the second dose of vaccine, the positivity rate increases over time: it is equal to
1.3% between 21 and 89 days,
2.4% between 90 and 119 days,
4.6% between 120 and 149 days,
10.3% between 150 and 179 days
15.5% after 180 days.
Compared to the first 90 days after the second vaccine dose, the risk of infection is 2.37 times higher after 90-119 days,
2.66 times higher after 120-149 days e
2.82 times higher beyond 150 days.
The researchers acknowledge that the interpretation of the data is limited by the observational design of the study and that the influence of other factors not considered in the analysis such as virus strain, number of family members and population density cannot be excluded. The analysis was designed to estimate the effect of the time elapsed since vaccination on the risk of contagion and did not assess the severity of these “revolutionary” infections in terms of the need for hospitalization, mechanical ventilation, mortality.
In any case, the study was conducted on a large number of people who received the same vaccine, so the results are robust enough to conclude that the protection induced by the two vaccine doses of Pfizer-BioNTech decreases over time and the risk of contagion it gradually increases after the first three months. The results suggest that consideration of a third dose of the vaccine in the near future may be warranted. In Italy it has just been decided to proceed with the third dose for all over 18s at least 5 months after the second dose.
November 25, 2021 (change November 25, 2021 | 11:13)
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