The effectiveness of the Pfizer / Bioentech covid vaccine, which is designed to prevent the spread of the deadly coronavirus, has dropped from 6% to 48% 6 months after the second dose.
A study was released on Monday, according to Reuters.
Health agencies in the United States also took this data into account when deciding whether a booster dose was required for the elderly and those at higher risk.
The data, published Monday in the Lancet Medical Journal, was released in August before an independent review or peer review.
Pfizer’s vaccine has been 90 percent effective for at least six months in preventing coronavirus hospitalization and death, and the study shows that it is almost equally effective against highly contagious delta species.
Studies have also shown that the effectiveness of the vaccine decreases after 6 months, not because of the more contagious type.
When the Pfizer vaccine was first administered, researchers at Pfizer and Kaiser Permanent obtained data on the effectiveness of the vaccine by looking at digital records of the health information of about 3.4 million members in Southern California from December 2020 to August this year.
“Research shows that the Pfizer / Bioentech vaccine is effective against all types of coronaviruses that are now a concern, including Delta,” said Lewis Joder, senior vice president and chief medical officer at Pfizer Vaccine.
Lack of information about those whose health information has been obtained, their occupations and whether they follow the instructions to wear masks may be a limitation of the study. From this information, it was possible to get an idea of how many people could be exposed to the virus.
The study found that one month after taking two doses of the highly contagious delta type, the effectiveness of the vaccine was 93 percent, and after four months it dropped to 53 percent.
Against other types, the effectiveness dropped from 96 percent to 6 percent over the same period.
“For us, the results of this study indicate that the Delta type is not a type capable of completely evading vaccine protection,” said Sarah Turtoff of the Southern California Research and Evaluation Division at Kaiser Permanente, head of the research team.
The U.S. Food and Drug Administration recently approved Pfizer / Bioentech booster doses for the elderly and people at high risk of infection.
However, scientists have asked for more data to check whether this dose will be applicable to everyone.