The Pfizer COVID-19 vaccine turned negatively effective after five months, according to a new study. Researchers with the U.S. Centers for Disease Control and Prevention (CDC) analyzed test results from sites across the United States and determined that the vaccine was 60 percent effective two to four weeks after 12- to 15-year-olds got the second of the two-dose primary regimen.
But the effectiveness, measured against symptomatic illness, quickly plummeted, hitting 20 percent around month two and zero around month five. After that, recipients in the age group were more likely to be infected by COVID-19.
Vaccine effectiveness “was no longer significantly different from 0 during month 3 after the second dose,” as per the study. Pfizer, its partner BioNTech, and the CDC didn’t respond to requests for comment based on the reports.
In another study, researchers reported the gap of infection and hospitalization risk between unvaccinated and vaccinated youth narrowing over time, with vaccinated 5- to 11-year-olds being infected at a rate of 62 per 100,000 and unvaccinated being infected at a rate of 70 per 100,000.
The protection also waned considerably against hospitalization over time, researchers found. They said that the findings support “efforts to increase vaccination coverage in children and adolescents.