High levels of strong antibodies following vaccination are linked to a lower risk of illness, according to real-world evidence from a medical centre.
According to a study of thousands of health-care professionals who received the Pfizer–BioNTech jab1, people who are fully vaccinated against COVID-19 are less likely to become infected with the coronavirus if they have reasonably high levels of virus-blocking antibodies.
The findings add to a growing body of evidence that suggests a person’s level of ‘neutralising’ antibodies, which prevent SARS-CoV-2 from invading cells, might predict whether or not they will become infected.
A reliable predictor of protection, known as a correlate of protection, could assist regulators in approving new vaccines without the need for extensive clinical studies.
It could also assist them in determining the need for booster doses to protect against new virus strains.
According to Miles Davenport, an immunologist at the University of New South Wales in Sydney, Australia, the study “is a crucial step in further establishing the use of neutralisation titre as a correlate of protection.”
When SARS-CoV-2 breaks through
Data from over 11,500 fully vaccinated health-care professionals at Sheba Medical Center near Tel Aviv, Israel, was used in the study, which was published in The New England Journal of Medicine on July 28.
Between late January and late April 2021, extensive testing revealed 39 workers who had contracted SARS-CoV-2 despite being completely vaccinated.
All reported minor symptoms or none at all, but 6 weeks after diagnosis, 19 percent still had symptoms.
The authors were able to get antibody measures from 22 of the 39 workers who had ‘breakthrough’ infections, either on the day the infections were discovered or the week prior.
The researchers also looked at data from 104 completely vaccinated individuals who were age-matched to infected workers but did not become ill.
According to Davenport, the comparison revealed that individuals who became sick had reduced levels of neutralising antibodies, which is the first direct proof of this effect.
The findings back up prior evidence from the Oxford–AstraZeneca vaccine’s clinical trials.