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Editorial

What you need to know about the Delta variant

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I’ve been hearing recently from friends and colleagues concerned about the ability of the Delta variant to cause “breakthrough infections” in those fully vaccinated and what this means.
First, almost all of the hospitalizations, intubations and deaths are now occurring in those not vaccinated. Vaccinated individuals may carry and transmit the virus, but they are not suffering serious disease, except for those with concomitant immunosuppressant conditions such as cancer, transplantation or autoimmune disease patients taking immunosuppressive drugs.
To understand this, let’s briefly review how COVID-19 vaccines stimulate the immune system to start building an immune response by making neutralizing antibodies against the spike protein, which is the first line of defense that protects us from natural infection. Data shows that this short-term neutralizing antibody response is quick and persists at clinically protective levels for at least eight months (eg, humoral immunity), while the longer-term protection is due to cellular immunity mediated by T cells.
Despite causing a surge in infections this summer that has resulted in thousands of hospitalizations and deaths among the unvaccinated, the Delta variant is not particularly good at evading the neutralizing antibodies generated by vaccination, according to a study by researchers at Washington University School of Medicine in St. Louis published recently in the journal Immunity. Thus, those fully vaccinated are well protected from serious disease, hospitalization and death for at least the first eight months or perhaps longer.

Taking this one step further, many are wondering what level of vaccine-induced neutralizing antibody production is needed to stimulate a clinically meaningful long-term T-cell response.
A recent paper published in Nature Communications determined that antibody levels above the threshold titer of 0.1 ug/ml and a median level 0.45 ug/ml are considered above the threshold needed to stimulate a vigorous antibody and T-cell response. Vaccine-induced SARS-CoV-2 specific T cell responses were only observed in subjects that elicited specific antibody titers above these thresholds.
Many people will need a booster shot to maintain these critical antibody levels over time and the immunocompromised will need a booster shot even sooner.
David Segarnick Ph.D. is senior vice president, Medical & Scientific Services, Evolution Health Group, Pearl River, N.Y., and assistant professor pharmacology, physiology and neuroscience at Rutgers Medical School, Newark, N.J. He lives in Upper Black Eddy.


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