On Monday, the U.S health agencies published data revealing that the effectiveness of the Pfizer Inc /BioNTech SE vaccine in preventing infection by the coronavirus dropped to 47% from 88% six months after the second dose.
This data was analyzed when the U.S. health agencies held a meeting to consider and decide on the need for booster shots, according to Reuters.
The data, which was published in the Lancet medical journal, revealed that the vaccine’s effectiveness in preventing hospitalization and death remained high at 90% for at least six months, including against the Delta variant of the coronavirus.
What this means
According to researchers, the drop in the effectiveness of the Pfizer vaccine is due to waning efficacy, rather than more contagious variants.
This data was obtained through the study of electronic health records of roughly 3.4 million people who were members of Kaiser Permanente Southern California between December 2020, when the vaccine first became available, and August of 2021.
However, a potential limitation of the study was a lack of data on the adherence of the study population to masking guidelines and their various occupations, which is believed could have influenced the frequency of testing and the likelihood of exposure to the virus.
The researchers who undertook this study are from Pfizer and Kaiser Permanente.
The study leader, Sara Tartof said, “To us, that suggests Delta is not an escape variant that is completely evading vaccine protection”.
“If it was, we would probably not have seen high protection after vaccination, because vaccination would not be working in that case. It would start low, and stay low”, she added.
The chief medical officer at Pfizer and senior vice president, Luis Jodar commented saying, “Our variant-specific analysis clearly shows that the (Pfizer/BioNTech) vaccine is effective against all current variants of concern, including Delta”.
The study revealed that vaccine efficacy against the Delta variant was 93% after the first month, but however, declined to 53% after the fourth month. Compared to other variants, however, the efficacy of the vaccine, waned by 30% to 67% from 97%.
Recently, the U.S. Food and Drug Administration (FDA) authorized the use of a booster dose of the Pfizer/BioNTech vaccine for older adults aged 65 and above and immunocompromised people who are at higher risks of the infection in the U.S.
In addition, scientists have called for more data to support the decisions on whether vaccine booster shots should be recommended for all age brackets.
