New research from Israel’s Sheba Medical Center demonstrates the waning of COVID-19 antibodies in the months following reception of two vaccine doses.
The study, published Wednesday in the New England Journal of Medicine, followed 5,000 medical personnel at the hospital who were under observation for a six-month period after getting the two vaccine doses.
It observed a clear, significant decrease in both IgG and neutralizing antibodies over that period.
Researchers reported a significant drop over the first three months, followed by a more moderate decline over the next three months. Women generally developed a better initial antibody count than men and were thus somewhat better protected after a six-month period.
The study found that after six months, a young healthy woman’s odds of losing her ability to neutralize the pathogen was 2.5% and a woman over 65% was at 6%; for men, it was 4% and 15% respectively.
Meanwhile, for immunocompromised individuals, the odds were far worse: 30% for women and 50% for men (over 65) and 18% for women and 24% for men (under 45).
“We managed to build a model that presents the odds of specific populations to have various antibody levels,” said researcher Dr. Gili Regev-Yochay. “Based on this model, in the future we can try to assess the odds of mild or severe illness… and determine the necessary treatment.”
Oddly, the research found that antibody levels in overweight persons — who generally are more susceptible to severe illness — remained higher than in others at the end of six months.
Regev-Yochay said this data point would need to be examined further, and did not necessarily mean they were better protected.
The drop in immunity against COVID-19 some six months after vaccination has led Israel to embark on its current booster campaign, meant to bolster protection half a year after the first two doses. Health officials believe the drop in immunity allowed the significant spread of the Delta variant of the coronavirus in the population in recent months, leading to Israel’s fourth wave which is now waning.