You can have gradual increased COVID risk after second Pfizer vaccine dose

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In a new study from the Research Institute of Leumit Health Services in Israel, researchers found a gradual increase in the risk of COVID-19 infection from 90 days after receiving a second dose of the Pfizer-BioNTech vaccine.

The study was carried out by. Israel was one of the first countries to roll out a large scale COVID-19 vaccination campaign in December 2020, but which has seen a resurgence of infections since June 2021.

The findings confirm that the Pfizer-BioNTech vaccine provided excellent protection in the initial weeks after vaccination, but suggest that protection wanes for some individuals with time.

Across the world, large scale COVID-19 vaccination campaigns are helping to control the spread of the virus, but even in countries with high vaccination rates, breakthrough infections can occur, which scientists think is due to a gradual loss of immunity over time.

In the study, the team examined electronic health records for 80,057 adults (average age 44 years) who received a PCR test at least three weeks after their second injection, and had no evidence of previous COVID-19 infection.

Of these 80,057 participants, 7,973 (9.6%) had a positive test result. The rate of positive results increased with time elapsed since a second dose.

For example, across all age groups, 1.3% of participants tested positive 21-89 days after a second dose, but this increased to 2.4% after 90-119 days; 4.6% after 120-149 days; 10.3% after 150-179 days; and 15.5% after 180 days or more.

And after taking account of other potentially influential factors, the researchers found a strongly increased risk of infection with time elapsed since a second dose.

Compared with the initial 90 days after a second dose, the risk of infection across all age groups was 2.37-fold higher after 90-119 days; 2.66-fold higher after 120-149 days; 2.82-fold higher after 150-179 days; and 2.82-fold higher after 180 days or more.

The researchers conclude that in individuals who received two doses of the Pfizer-BioNTech vaccine, protection seemed to decrease over time, and the risk of breakthrough infection increased progressively compared with the protection provided during the initial 90 days.

If you care about COVID vaccines, please read studies about ‘version 2.0’ of COVID-19 vaccine quickly boosts immune system and findings of if you have a weakened immune system, consider 3rd COVID-19 vaccine dose.

For more information about COVID vaccines, please see recent studies about COVID-19 vaccines are 66% effective fighting against Delta variant and results showing that what you should know about COVID-19 booster shots and third vaccine doses.

The study is published in The BMJ.

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