COVID-19 Vaccine News: Moderna Variant Vaccine Begins Human Testing, AZ Put on Hold in Denmark


Patients in a Phase II trial have begun receiving Moderna’s vaccine against the SARS-CoV-2 variant first identified in South Africa, the company announced. The modified vaccine, mRNA-1273.351, is being tested out of an abundance of caution, despite the fact that previous data has shown that the company’s marketed mRNA-1273 vaccine produces neutralizing titers against all relevant variations, the company said.

Similarly inspired by caution, Denmark announced it is temporarily stopping vaccinations with AstraZeneca’s ABV5300 while the European Medicines Agency (EMA) investigates a possible link between the COVID-19 vaccine and severe blood clots. At least six other European countries are following suit.  Two people in Denmark and Austria have died after getting the vaccine, and a third person was hospitalized with pulmonary embolism.

Moderna Covers Its Bases

In vitro data posted online by Cambridge, Mass.-based in January–but not yet peer reviewed–showed that while mRNA-1273 produced neutralizing antibodies against both the U.K. and South Africa variants, the vaccine was unlikely to have the same 94% efficacy in preventing COVID-19 seen in its Phase III trials.

Moderna is now testing three different boosters in its Phase II trial, including a 20 µg dose of mRNA-1273.351 against the more-contagious B.1.351 variant, a 50 µg dose, and a multivalent booster combining mRNA-1273.351 and mRNA-1273. The boosters will be tested in 60 people who have previously received two doses of mRNA-1273.

The company also announced that the National Institute of Allergy and Infectious Disease (NIAID), part of the National Institutes of Health (NIH), will run a Phase I safety trial of its vaccines in parallel. The NIAID trial will test mRNA-1273 and mRNA-1273.351 combinations in series, and also as single boosters in patients who have been previously vaccinated with mRNA-1273.

Denmark Takes A Pause

“At present, it cannot be concluded whether there is a link between the vaccine and the blood clots,” said the Danish Health Authority in a statement, stressing that it is only pausing for 14 days—­not halting–distribution of the AstraZeneca vaccine.

The announcement comes days after Austria suspended use of a single batch of ABV5300 linked to two people who later developed severe clots and embolism, respectively. The batch contained 1 million doses delivered to 17 EU countries. The EMA said at the time that a quality defect in the batch is “unlikely” and that the number of thromboembolic events seen in Europe among people receiving the vaccine was consistent with the general population.

“There is good evidence that the vaccine is both safe and effective,” said Søren Brostrøm, director of the National Board of Health in Denmark. “But both we and the Danish Medicines Agency have to react to reports of possible serious side effects, both from Denmark and other European countries,” he said.

Norway announced a similar pause, while Estonia, Latvia, Lithuania, and Luxembourg are following Austria’s lead and suspending use of the specific batch.

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