How long does COVID-19 vaccine-generated immunity last? New laboratory results provide a partial answer to that question.
Antibodies generated by a currently available COVID-19 vaccine declined over time, but remained at high levels in 33 study participants 6 months after vaccination, according to data published Tuesday in the New England Journal of Medicine.
The results could begin to inform public health decisions about COVID-19 booster vaccinations and how frequently people should receive them. In older study participants, antiviral antibody activity tended to decay more rapidly than in those aged 18-55.
Emory Vaccine Center’s Mehul Suthar, co-lead author of the brief report, said that the “correlates of protection” are not yet known from COVID-19 vaccine studies – that is, what levels of antiviral antibodies are needed to fend off infection. Other forms of immunity, such as T cells, could be contributing to antiviral protection as well.
He cautioned that the decay in antibody activity over time – not surprising in itself – may combine with increased prevalence of emerging SARS-CoV-2 variants that may allow viruses to escape the immune system’s pressure.
“Still, these are encouraging results,” Suthar says. “We are seeing good antibody activity, measured three different ways, six months after vaccination. There are differences between age groups, which are consistent with what we know from other studies.”
Amidst the tumult in the nation’s capital, a quieter reckoning was taking place this week for the Moderna COVID-19 vaccine clinical trial. Lab Land has been hearing from Emory-affiliated study participants that they’re finding out whether they received active vaccine or placebo.
For example, Emory and Grady physician Kimberly Manning, who had written about her participation in the Moderna study in a Lancet essay, posted on Twitter Tuesday. She discovered she had received placebo, and then was offered active vaccine.
“Companies have said that they feel an ethical obligation to deliver vaccine to placebo recipients; the FDA and experts at its advisory panel have debated whether this obligation even exists. Instead, they argue, offering vaccine to volunteers receiving placebo limits the quality of the data about the vaccine’s long-term efficacy and side effects.”
A plan to keep participants in the study under a blinded crossover design was floated, but not implemented. Some participants have said they sensed from the start, based on temporary unpleasant side effects, whether they had received active vaccine or placebo.