Covid-19 roundup: Moderna vaccine kicks up antibodies against Delta variant; UK study validates mix-and-match approach for Pfizer-AstraZeneca
In an continued effort to monitor the effectiveness of its Covid-19 vaccine, Moderna has rolled out the latest slate of neutralization data against different variants — including the Delta variant first identified in India.
The data were published on the preprint server bioRxiv as the Delta variant has engulfed a number of countries, leading to resurgence of infections.
Deploying a well-documented method, investigators took blood samples from eight participants of Moderna’s Phase I trial one week after their second dose of mRNA-1273, and pitted them against pseudovirus engineered to bear features of variants of concerns (VOCs), including the “the Beta variant (B.1.351, first identified in South Africa), three lineage variants of B.1.617 (first identified in India), including the Kappa (B.1.617.1) and the Delta variants (B.1.617.2); the Eta variant (B.1.525, first identified in Nigeria); and the A.23.1 and A.VOI.V2 variants first identified in Uganda and Angola, respectively.”
They then compared the neutralizing antibody levels to that of the wild type virus first discovered in Wuhan.
Among VOCs tested, serum-elicited neutralization of the B.1.1.7 (Alpha) variant was comparable to D614G; a range of reduced neutralization titers compared to D614G were observed for other VOCs including the B.1.351 (Beta), B.1.617.2 (Delta), and P.1 (Gamma) variants, with reductions ranging from 2.1-fold to 8.4-fold.
To Moderna CEO Stéphane Bancel, the data are “encouraging” in that they support his vaccine’s status as an effective “primary series vaccine” even against newly detected variants.
The biotech is also studying a multivalent booster candidate, which they’re calling mRNA-1273.211, containing both the original vaccine and a new jab designed to target the Beta variant. — Amber Tong
UK study validates mix-and-match approach for Pfizer-AstraZeneca
Some of the first data for a mix-and-match vaccine regimen are in, and they’re encouraging for the UK and much of Europe.
The Oxford study, called Com-COV, found that administering a shot of Pfizer/BioNTech vaccine as a second dose after the AstraZeneca vaccine produced stronger immune responses than giving two shots of the AstraZeneca vaccine.
The results, which focused on dosing at four-week intervals, are perhaps unsurprising given that Pfizer’s vaccine has appeared more effective across the board than the AstraZeneca jab. But, given the persnickety, unpredictable nature of the immune system, they were not assured.
The results provide the first good data to support what the UK and broad swaths of Europe are already doing: Amid shortages of AstraZeneca doses and concerns about its connection to rare but serious blood clots, those nations allowed or encouraged people who received a shot of their jab to use an mRNA shot for their second dose.
The study indicated, though, that not all combinations were created equal. A shot of AstraZeneca then a shot of Pfizer produced a better antibody response, but a shot of Pfizer then AstraZeneca produced a higher T cell response.
The same study is now examining the results of giving the vaccines 12 weeks apart. That schedule aligns with how the vaccines have been rolled out in the UK and some data suggest the AstraZeneca vaccine works better when given at longer intervals. — Jason Mast
Leading Chinese vaccine proves safe in children
One of the leading Chinese-made vaccines appears to be safe and to induce antibodies in children, potentially adding another tool, alongside the Pfizer and Moderna shots, to protect those under the age of 18.
Sinovac published data in The Lancet Monday showing that its inactivated virus vaccine elicited antibodies in 96% of 550 children and adolescents in China. Mild or moderate adverse events were relatively uncommon compared to other vaccines, with 26% of volunteers reporting one such event, and there was only one serious adverse event — a case of pneumonia.
Although Sinovac is one of the least efficacious Covid-19 vaccines authorized in any country, with Phase III data showing around 51% protection against symptomatic disease, it still appeared largely protective against hospitalization or death and has become a key pillar of vaccination campaigns in countries across Asia. The company claims to have delivered more than 600 million doses as of June 1. — Jason Mast
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