COVID-19 vaccine effectiveness against both infection and death was studied in three US approved jabs – the Pfizer-BioNTech and Moderna mRNA shots, and the Janssen viral vector vaccine.
Having analyzed data from 780,225 US veterans of different ages and sexes between February and October, researchers came to a disturbing conclusion.
Vaccine protection against COVID-19 infection dropped from 89.2% at its highest to a low of 13.1%, according to a joint study by the Public Health Institute, the Veterans Affairs Medical Center, and the University of Texas Health Science Center, published in the Science journal on Thursday.
While effectiveness against infection in March was 89.2% for Moderna, 86.9% for Pfizer, and 86.4% for Janssen, by September there were massive declines to 58%, 43%, and 13% respectively.
The emergence and dominance of the Delta strain of the virus during the time of the study may have played a role, researchers said, adding that vaccine protection waned across all studied age groups.
More than 26,000 positive PCR tests occurred in some 498,000 fully vaccinated veterans.
The authors said the pattern of breakthrough infections shows a “worrisome temporal trend.” While the analysis covers 2.7 percent of the US population, other domestic and international studies have shown significantly waning efficacy.
On a brighter note, vaccine effectiveness against hospitalization and death remained high.
As breakthrough infections, hospitalizations, and deaths continue to emerge in fully vaccinated people, there is “an urgent need to reinstate multiple layers of protection, such as masking and physical distancing – even among vaccinated persons,” the scientists warn.