Data has shown that the effectiveness of the Pfizer/BioNTech vaccine against the coronavirus dropped to 47% from 88% six months after the second dose, according to a study referenced by U.S. health agencies when deciding to grant booster doses of the vaccine. Data published on Monday in The Lancet medical journal indicated that an analysis of the vaccine's effectiveness in preventing symptomatic infections that require hospital admission or death due to COVID-19 showed it remains effective at a rate of 90% for at least six months, even in the face of the rapidly spreading Delta variant. Researchers stated that the decline in effectiveness over time is the reason, rather than the emergence of more transmissible strains of the virus.
The data indicates that vaccine effectiveness against the Delta variant was 93% after the first month but fell to 53% after four months. In the face of other coronavirus variants, effectiveness dropped to 67% from 97%. The U.S. Food and Drug Administration had authorized the use of a booster dose of the Pfizer/BioNTech vaccine for seniors and some Americans at higher risk of infection. Scientists have called for more data before recommending booster doses for everyone who has been vaccinated.
