Pfizer/BioNTech Covid-19 vaccine: Protection against infection offered by fourth dose wanes quickly, Israeli study finds

The study, published Tuesday in the New England Journal of Medicine, analyzed the health records of more than 1.25 million vaccinated people in Israel who were 60 years of age or older from January to March 2022, a time when the variant of the Omicron coronavirus was the dominant strain.

The rate of severe COVID-19 infection in the fourth week after a fourth dose of the vaccine was lower than in people who received only three doses by a factor of 3.5.

However, the protection against serious illness did not appear to decrease in the six weeks after the fourth injection, although the study period was not long enough to determine exactly how long this protection lasts.

The confirmed infection rate in the fourth week after the fourth dose was lower than in the three-dose group by a factor of 2. There appeared to be maximal protection against Omicron in the fourth week after vaccination, but the ratio of Rates fell to 1.1 by week eight, suggesting that “protection against confirmed infection declines rapidly,” the study says.

The protection provided by any vaccine naturally diminishes, but a vaccine primes the immune system to produce protective antibodies if it encounters threats later on.

Currently available Covid-19 vaccines were manufactured to protect against the original strain of the virus. Omicron is significantly different and therefore the vaccines have lost some of their effectiveness. Israel and the US are among the governments that have suggested the fourth vaccine for certain people who are at high risk of getting seriously ill, such as the elderly.

Last week, the FDA expanded its emergency use authorization to allow adults age 50 and older to receive a second booster shot as early as four months after their first booster of a Pfizer or Moderna vaccine. People with certain immunodeficiencies can also get a fourth dose in the US, but debate continues over whether one is needed for the general population.
The US Food and Drug Administration’s independent vaccine committee is meeting Wednesday to discuss what the country’s booster strategy should be. Some experts have suggested that the Covid-19 vaccine could become an annual shot like the flu shot.

There are limits to what the new research can say about the need for a fourth dose of vaccine. It compares only the protection provided by the third and fourth doses, so it does not include unvaccinated people for comparison. It also doesn’t add to the debate about whether people under 60 may need a fourth dose. Previous research in Israel showed that a fourth dose didn’t do much in healthy younger populations, at least in terms of protection against infection.

For confirmed infection, “a fourth dose appears to provide only short-term protection and modest absolute benefit,” the researchers wrote. But when it comes to a serious infection, the fourth injection seems to help.

“Overall, these analyzes provide evidence for the effectiveness of a fourth dose of vaccine against severe disease caused by the Omicron variant compared to a third dose given more than four months later,” the study says.

Even with this news, it’s unclear how many eligible people will receive a fourth COVID-19 vaccine. About 66% of the US population has received at least one Covid-19 vaccine, but only 30% of people are fully vaccinated with a booster dose, according to the Centers for Disease Control and Prevention. of US Diseases

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