Moderna data suggests effectiveness of its shot against emerging variants
Its mRNA shot generated neutralizing antibodies against the Delta as well as the Beta and Eta strains, variants first found in South Africa and Nigeria, respectively, reported Moderna.
The US biotech said the results were based on the blood serum of eight participants one week after they received the second dose of the vaccine.
The data has not been subject to peer review, as of yet; the results were submitted as a preprint to bioRxiv.
“We remain committed to studying emerging variants, generating data and sharing it as it becomes available,” said Moderna CEO Stephane Bancel. “These new data are encouraging and reinforce our belief that the Moderna COVID-19 Vaccine should remain protective against newly detected variants.”
The biotech continues to evaluate mRNA-1273.211, a multivalent booster candidate which combines a 50-50 mix of mRNA-1273, Moderna’s authorized vaccine against ancestral strains, and mRNA-1273.351 in a single vaccine at several dose levels in an ongoing trial.
Long-lasting immune response
Meanwhile, a peer-reviewed study, published yesterday in Nature, concluded that both COVID-19 mRNA vaccines developed by Moderna and Pfizer-BioNTech are likely to offer long-lasting protection against COVID-19.
The study from researchers at Washington University School of Medicine in St Louis, found evidence that the immune response to such vaccines is both strong and potentially long-lasting.
Nearly four months after the first dose, people who received the Pfizer vaccine still had “germinal centers” in their lymph nodes generating immune cells directed against SARS-CoV-2, reported the authors.
Germinal centers form as the result of natural infection or vaccination; a better germinal center response may equal a better vaccine, said the researchers.
Senior author Ali Ellebedy, PhD, an associate professor of pathology and immunology, of medicine and of molecular microbiology, commented: "The longer we have a germinal center, the stronger and more durable our immunity will be because there's a fierce selection process happening there, and only the best immune cells survive. We found that germinal centers were still going strong 15 weeks after the vaccine's first dose. We're still monitoring the germinal centers, and they're not declining; in some people, they're still ongoing.”
Ultrasound-guided sampling
In terms of background, the team wanted to assess whether mRNA vaccines induce a good germinal center response, with Ellebedy and co-authors starting the study once the first COVID-19 vaccine became available in the US in mid-December 2020.
They enlisted the help of co-authors Dr Sharlene Teefey, and Dr William Middleton, both professors of radiology, to perform ultrasound-guided sampling of the minuscule germinal centers in lymph nodes in the armpit.
They explained that Teefey and Middleton extracted cells from 14 people who received the Pfizer vaccine. Samples were obtained three weeks after the first dose (just prior to administration of the second dose), and at weeks four, five and seven. Ten of the participants gave additional samples 15 weeks after the first dose. None of the participants previously had been infected with the virus that causes COVID-19.
Three weeks after the first dose, all 14 participants had formed germinal centers with B cells producing antibodies that target a key SARS-CoV-2 protein. The response expanded greatly after the booster shot and then stayed high. Even 15 weeks after the first dose, eight of 10 people still had detectable germinal centers containing B cells targeting the virus, they found. "This is evidence of a really robust immune response.”
